diff --git a/Hs2lib.cabal b/Hs2lib.cabal
--- a/Hs2lib.cabal
+++ b/Hs2lib.cabal
@@ -1,5 +1,5 @@
 Name:           Hs2lib
-Version:        0.5.0
+Version:        0.5.1
 Cabal-Version:  >= 1.10
 Build-Type:     Custom
 License:        BSD3
diff --git a/LIMITS.txt b/LIMITS.txt
--- a/LIMITS.txt
+++ b/LIMITS.txt
@@ -1,3 +1,6 @@
+Version 0.5.1
+ - Library bug fix which cauzed an error in marshalling
+
 Version 0.5.0
  - Added support for memory leak tracing with the --debug flag
  % Added support for qualified importing. It is now possible to export
diff --git a/WinDll/Lib/NativeMapping_Base.cpphs b/WinDll/Lib/NativeMapping_Base.cpphs
--- a/WinDll/Lib/NativeMapping_Base.cpphs
+++ b/WinDll/Lib/NativeMapping_Base.cpphs
@@ -232,6 +232,9 @@
    
 -- | Tranform functions to and from the correct types
 --   TODO: Update this variant to use the impure variants, This will be an issue..
+--   TODO: Can this even be defined using the native functions?
+--   This instance can't be generated. It'll stay here for now, buy it can only
+--   be used by types which define toFFI/fromFFI instead of toNative/fromNative
 instance (FFIType a b, FFIType c d) => FFIType (a -> c) (b -> d) where
    toFFI   _ST_ f x = toFFI   _ST_ (f (fromFFI _ST_ x))
    fromFFI _ST_ f x = fromFFI _ST_ (f (toFFI _ST_ x))
@@ -239,16 +242,20 @@
 -- | I decided to use a CAString because on windows this gives me a constant 16 value
 instance FFIType String CWString where
     toNative   = RECORDM(__FILE__, __LINE__, "newCWString" , newCWString)
-    fromNative _ST_ ptr = (RECORD( __FILE__, __LINE__, "peekCWString", id)) _ST_ ptr
-                        >>   peekCWString ptr
-                        >>=  \str -> freeFFI _ST_ "" ptr
-                        >>   return str
+    fromNative _ST_ ptr = do {(RECORD( __FILE__, __LINE__, "peekCWString", id)) _ST_ ptr;
+                              str <- peekCWString ptr;
+                              freeFFI _ST_ "" ptr;
+                              return str;}
+                        
     freeFFI    = FREE(   __FILE__, __LINE__, "freeCWString", F.free)
     
 -- | Intermediate conversion instance for storing values of arrays
 instance (Storable a, FFIType b a) => FFIType [b] (Ptr a) where
-    toNative _ST_   = (RECORDM(__FILE__, __LINE__, "newArray", newArray)) _ST_ . map (toFFI _ST_)    
-    fromList _ST_ x = fmap (map (fromFFI _ST_)) . (RECORD(__FILE__, __LINE__, "peekArray", id) >>= peekArray (fromFFI _ST_ x)) _ST_
+    toNative _ST_   = (RECORDM(__FILE__, __LINE__, "newArray", (\val -> newArray =<< mapM (toNative _ST_) val))) _ST_    
+    fromList _ST_ x ptr = do {(RECORD(__FILE__, __LINE__, "peekArray", id)) _ST_ ptr;
+                              i <- fromNative _ST_ x;
+                              v <- peekArray i ptr;
+                              mapM (fromNative _ST_) v;}
     
 -- | Another simple identity instance, I really need to get that overlapping instances
 --   looked at.
@@ -282,8 +289,8 @@
     
 -- | Convert between FastString and CWString
 instance FFIType FastString CWString where
-    toFFI   _ST_ = toFFI _ST_.unpackFS
-    fromFFI _ST_ = mkFastString.fromFFI _ST_
+    toNative   _ST_ = toNative _ST_ . unpackFS
+    fromNative _ST_ = (mkFastString `fmap`) . fromNative _ST_
     
 -- | Fix integers from the machine dependend values to fixed 32bit values
 instance FFIType Int CInt where
@@ -310,9 +317,9 @@
 instance Storable a => FFIType [a] (Ptr a) where
     toNative = RECORDM(__FILE__, __LINE__, "newArray", newArray) --fmap castPtr . new -- newArray
 #ifdef DEBUG
-    fromList st ic ptr = (RECORD( __FILE__, __LINE__, "peek", id)) st ptr >> peekArray (fromFFI st ic) ptr --const (peek . castPtr) --peekArray
+    fromList st ic ptr = (RECORD( __FILE__, __LINE__, "peek", id)) st ptr >> fromNative st ic >>= \i -> peekArray i ptr --const (peek . castPtr) --peekArray
 #else
-    fromList = peekArray . fromFFI --const (peek . castPtr) --peekArray
+    fromList ic ptr = fromNative ic >>= \i -> peekArray i ptr --const (peek . castPtr) --peekArray
 #endif
     freeFFI     = FREE(   __FILE__, __LINE__, "freeArray", F.free)
     -- | Intermediate conversion instance for storing values of arrays
@@ -372,6 +379,7 @@
     fromFFI = _CONST_ toInteger
     
 -- | Instance for Functor classes
+--   TODO: rewrite this.
 instance (Functor f, FFIType a b) => FFIType (f a) (f b) where
     toFFI   _ST_ = fmap (toFFI   _ST_)
     fromFFI _ST_ = fmap (fromFFI _ST_)
diff --git a/WinDll/Version/Hs2lib.hs b/WinDll/Version/Hs2lib.hs
--- a/WinDll/Version/Hs2lib.hs
+++ b/WinDll/Version/Hs2lib.hs
@@ -19,7 +19,7 @@
 
 -- | Version Number
 verNum :: [Int]
-verNum = [0,5,0]
+verNum = [0,5,1]
 
 -- | Version string
 verStr :: String