/usr/share/doc/ghc/html/libraries/.pkg-dir.cache /usr is supposed to be read only. Any chance putting this in /var/lib/ghc and setting up a symbolic link?
We should probably move %_libdir/ghc-%version/package.conf.d/package.cache too. Will also check to see what Debian does - I think they might be using /etc/ghc/.
Or maybe rpm install scripts are exempt?
This should be fixed in ghc-7.0.1-3.fc15. Thanks for the report.
I believe this is fixed now for some time in rawhide. Please reopen if there is still any problem.