getDirectoryContents fails in GHC 6.5 snapshots, works in GHC 6.4.1 snapshots

This bug breaks Cabal 1.0 and Cabal 1.1.1.
Expected results: passed
Actual results: *** Exception: c:\: getDirectoryContents: failed (No error)

The GHC 6.4.1 snapshot was downloaded a week ago; GHC 6.5 is the
snapshot from July 18th.

Main.lhs:
> import System.Directory(getDirectoryContents)
>
> main = do
>   x <- getDirectoryContents "c:\\"
>   putStrLn "passed"
>   return ()   

C:\>ver
Microsoft Windows XP [Version 5.1.2600]

C:\>set path=c:\software\ghc-6.4\bin
C:\>ghc --version
The Glorious Glasgow Haskell Compilation System, version 6.4

C:\>runghc Main.lhs
passed

C:\>set path=c:\software\ghc-6.4.1\bin

C:\>ghc --version
The Glorious Glasgow Haskell Compilation System, version 6.4.1

C:\>runghc Main.lhs
passed

C:\>set path=c:\software\ghc-6.5\bin

C:\>ghc --version
The Glorious Glasgow Haskell Compilation System, version 6.5

C:\>runghc Main.lhs
*** Exception: c:\: getDirectoryContents: failed (No error)