diff --git a/CHANGELOG.md b/CHANGELOG.md
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,15 @@
 #Change Log
 
+##0.5.3
+
+###new features
+* SessionNotCreated constructor added to FailedCommandType
+* new command deleteCookieByName added
+
+###bug fixes
+* asyncJS now properly distinguishes between a null return and a script timeout
+* fixed a change in waitWhile causing the opposite of expected behavior
+
 ##0.5.2
 ###API changes
 * added many new Internet Explorer capabilities
diff --git a/TODO b/TODO
--- a/TODO
+++ b/TODO
@@ -2,8 +2,6 @@
 
 -- fix loadProfile so that it doesn't cause an overlap with user addExtension calls
 
--- add support for new experimental IE capabilities
-
 -- add support for Opera profiles
 
 -- improve documentation
diff --git a/src/Test/WebDriver/Commands.hs b/src/Test/WebDriver/Commands.hs
--- a/src/Test/WebDriver/Commands.hs
+++ b/src/Test/WebDriver/Commands.hs
@@ -37,7 +37,7 @@
        , focusFrame, FrameSelector(..)
          -- * Cookies
        , Cookie(..), mkCookie
-       , cookies, setCookie, deleteCookie, deleteVisibleCookies
+       , cookies, setCookie, deleteCookie, deleteVisibleCookies, deleteCookieByName
          -- * Alerts
        , getAlertText, replyToAlert, acceptAlert, dismissAlert
          -- * Mouse gestures
@@ -148,7 +148,7 @@
 setScriptTimeout :: WebDriver wd => Integer -> wd ()
 setScriptTimeout ms =
   noReturn $ doSessCommand POST "/timeouts/async_script" (object msField)
-    `L.catch` \(_ :: SomeException) ->
+    `L.catch` \( _ :: SomeException) ->
       doSessCommand POST "/timeouts" (object allFields)
   where msField   = ["ms" .= ms]
         allFields = ["type" .= ("script" :: String)] ++ msField
@@ -217,11 +217,12 @@
 Javascript function timed out (see 'setScriptTimeout')
 -}
 asyncJS :: (WebDriver wd, FromJSON a) => [JSArg] -> Text -> wd (Maybe a)
-asyncJS a s = handle timeout $ fromJSON' =<< getResult
+asyncJS a s = handle timeout $ Just <$> (fromJSON' =<< getResult)
   where
     getResult = doSessCommand POST "/execute_async" . pair ("args", "script")
                 $ (a,s)
-    timeout (FailedCommand Timeout _) = return Nothing
+    timeout (FailedCommand Timeout _)       = return Nothing
+    timeout (FailedCommand ScriptTimeout _) = return Nothing
     timeout err = throwIO err
 
 -- |Grab a screenshot of the current page as a PNG image
@@ -365,8 +366,10 @@
 -- |Delete a cookie. This will do nothing is the cookie isn't visible to the
 -- current page.
 deleteCookie :: WebDriver wd => Cookie -> wd ()
-deleteCookie c = 
-  noReturn $ doSessCommand DELETE ("/cookie/" `append` urlEncode (cookName c)) Null
+deleteCookie c = noReturn $ doSessCommand DELETE ("/cookie/" `append` urlEncode (cookName c)) Null
+
+deleteCookieByName :: WebDriver wd => Text -> wd ()
+deleteCookieByName n = noReturn $ doSessCommand DELETE ("/cookie/" `append` n) Null
 
 -- |Delete all visible cookies on the current page.
 deleteVisibleCookies :: WebDriver wd => wd ()
diff --git a/src/Test/WebDriver/Commands/Wait.hs b/src/Test/WebDriver/Commands/Wait.hs
--- a/src/Test/WebDriver/Commands/Wait.hs
+++ b/src/Test/WebDriver/Commands/Wait.hs
@@ -61,16 +61,7 @@
 -- |Similar to 'waitUntil' but allows you to also specify the poll frequency
 -- of the 'WD' action. The frequency is expressed as an integer in microseconds.
 waitUntil' :: SessionState m => Int -> Double -> m a -> m a
-waitUntil' = wait' handler
-  where
-    handler retry = (`catches` [Handler handleFailedCommand
-                               ,Handler handleExpectFailed]
-                    )
-      where
-        handleFailedCommand e@(FailedCommand NoSuchElement _) = retry (show e)
-        handleFailedCommand err = throwIO err
-
-        handleExpectFailed (e :: ExpectFailed) = retry (show e)
+waitUntil' = waitEither id (\_ -> return)
 
 -- |Like 'waitUntil', but retries the action until it fails or until the timeout
 -- is exceeded.
@@ -80,34 +71,44 @@
 -- |Like 'waitUntil'', but retries the action until it either fails or
 -- until the timeout is exceeded.
 waitWhile' :: SessionState m => Int -> Double -> m a -> m ()
-waitWhile' = wait' handler
-  where
-    handler retry wd = do
-      b <- (wd >> return Nothing) `catches` [Handler handleFailedCommand
-                                            ,Handler handleExpectFailed
-                                            ]
-      maybe (return ()) retry b
-      where
-        handleFailedCommand e@(FailedCommand NoSuchElement _) = return (Just $ show e)
-        handleFailedCommand err = throwIO err
+waitWhile' =
+  waitEither  (\_ _ -> return ())
+              (\retry _ -> retry "waitWhile: action did not fail")
 
-        handleExpectFailed (e :: ExpectFailed) = return (Just $ show e)
 
+-- |Internal function used to implement explicit wait commands using success and failure continuations
+waitEither :: SessionState m =>
+               ((String -> m b) -> String -> m b)
+            -> ((String -> m b) -> a -> m b)
+            -> Int -> Double -> m a -> m b
+waitEither failure success = wait' handler
+ where
+  handler retry wd = do
+    e <- fmap Right wd  `catches` [Handler handleFailedCommand
+                                  ,Handler handleExpectFailed
+                                  ]
+    either (failure retry) (success retry) e
+   where
+    handleFailedCommand e@(FailedCommand NoSuchElement _) = return . Left . show $ e
+    handleFailedCommand err = throwIO err
+
+    handleExpectFailed (e :: ExpectFailed) = return . Left . show $ e
+
 wait' :: SessionState m =>
          ((String -> m b) -> m a -> m b) -> Int -> Double -> m a -> m b
 wait' handler waitAmnt t wd = waitLoop =<< liftBase getCurrentTime
-  where timeout = realToFrac t
-        waitLoop startTime = handler retry wd
-          where
-            retry why = do
-              now <- liftBase getCurrentTime
-              if diffUTCTime now startTime >= timeout
-                then
-                  failedCommand Timeout $
-                    "wait': explicit wait timed out (" ++ why ++ ")."
-                else do
-                  liftBase . threadDelay $ waitAmnt
-                  waitLoop startTime
+  where 
+    timeout = realToFrac t
+    waitLoop startTime = handler retry wd
+      where
+        retry why = do
+          now <- liftBase getCurrentTime
+          if diffUTCTime now startTime >= timeout 
+            then 
+              failedCommand Timeout $ "wait': explicit wait timed out (" ++ why ++ ")."
+            else do
+              liftBase . threadDelay $ waitAmnt
+              waitLoop startTime
 
 -- |Convenience function to catch 'FailedCommand' 'Timeout' exceptions
 -- and perform some action.
diff --git a/src/Test/WebDriver/Internal.hs b/src/Test/WebDriver/Internal.hs
--- a/src/Test/WebDriver/Internal.hs
+++ b/src/Test/WebDriver/Internal.hs
@@ -159,6 +159,7 @@
     30  -> e IMENotAvailable
     31  -> e IMEEngineActivationFailed
     32  -> e InvalidSelector
+    33  -> e SessionNotCreated
     34  -> e MoveTargetOutOfBounds
     51  -> e InvalidXPathSelector
     52  -> e InvalidXPathSelectorReturnType
@@ -233,6 +234,7 @@
                        | IMENotAvailable
                        | IMEEngineActivationFailed
                        | InvalidSelector
+                       | SessionNotCreated
                        | MoveTargetOutOfBounds
                        | InvalidXPathSelector
                        | InvalidXPathSelectorReturnType
diff --git a/webdriver.cabal b/webdriver.cabal
--- a/webdriver.cabal
+++ b/webdriver.cabal
@@ -1,5 +1,5 @@
 Name: webdriver
-Version: 0.5.2
+Version: 0.5.3
 Cabal-Version: >= 1.8
 License: BSD3
 License-File: LICENSE
@@ -30,7 +30,7 @@
   hs-source-dirs: src
   ghc-options: -Wall
   build-depends:   base == 4.*
-                 , aeson >= 0.6.2.0 && < 0.7
+                 , aeson >= 0.6.2.0 && < 0.8
                  , HTTP >= 4000.1 && < 4000.3
                  , mtl >= 2.0 && < 2.2
                  , network == 2.4.*
@@ -42,7 +42,7 @@
                  , directory == 1.*
                  , filepath == 1.*
                  , unordered-containers >= 0.1.3 && < 0.4
-                 , attoparsec == 0.10.*
+                 , attoparsec < 0.12
                  , monad-control == 0.3.*
                  , transformers-base >= 0.1 && < 1.0
                  , vector >= 0.3 && < 0.11