Distribution/Simple/InstallDirs.hs:267:36:
Not in scope: `dropDrive'

hartthoma@linuxpt:~/installs/cabal-head/cabal>ls -l `which ghc`
lrwxrwxrwx 1 root root 31 2007-08-20 11:08 /usr/local/bin/ghc -> /usr/local/bin/ghc-6.7.20070816

You'll need to upgrade the filepath library as well, since cabal depends on it, and a very recent version at that.

Thanks

Neil