Windows build again

Windows build is broken in a new way. When I run validate I end up with sh.exe processes that consume a full CPU forever. See the process log below. Note that these are not GHC processes: they are shells! I have no conception of what they are doing. Any ideas, or things I can to do gather more evidence? This is an up to date HEAD, with some small changes to GHC. I suppose I can try a completely clean HEAD, but I can't see how my changes could make the shell loop. Simon [cid:image003.jpg@01D2526B.A8994140]