hsc2hs tries to remove an open file
When building GHC on Windows, hsc2hs sometimes fails with
hsc2hs.exe: System\CPUTime_hsc_make.exe: removeFile: permission denied (Permission denied)
This is because it tries to remove a file it has open handle to. The error usually repeats per-machine and file, but what file and machine it shows up with, is random.
As a workaround, calls to removeFile can be removed, or exceptions catched.
From a mail by Brian Smith: http://www.haskell.org/pipermail/cvs-ghc/2006-September/031186.html