with Cygwin I get
Linking dist\build\cmu\cmu.exe ... C:\Program Files\Haskell Platform\2010.1.0.0\lib\..\mingw\bin \windres: can't open temporary file `\/cca04932.irc': No such file or directory
This sounds very much like a temporary-filename issue. The reported filename's lack of a valid directory specifier looks highly suspicious to me. Are your TEMP, TEMPDIR, TMP, and TMPDIR environment variables set? Are their values sensible? Do you have appropriate permissions on the directories they point to? These are the kinds of thing I usually need to check when setting up a new Cygwin build environment. Admittedly, we do not use cabal on Windows (firewall prevents it from working), but the other ghc tools generally seem to work without problems for us under Cygwin. Regards, Malcolm