Dreaded "... has stopped working" with LLVM back end on Win64

I'm using the 7.6.2 Win64 port to try to compile HEAD with the quick-llvm BuildFlavour (I'm using LLVM 3.1). This entails setting -optlc-mtriple=x86_64-w64-mingw32 since the LLVM back-end doesn't output the right triple when producing .ll files. Unfortunately I get the dreaded "ghc-cabal.exe has stopped working" pop-up dialog as soon as ghc-cabal.exe is invoked. Interestingly, ghc-cabal.exe behaves as expected when invoked with no command line arguments. I have no idea where to start with this one. Any hints? Has anyone ever used the LLVM back end on Win64 (I'm guessing not). Thanks, Geoff