I too got lots of issues after installing aptitude, then tries to find the issue in console and found out that dpkg (the application that handles actual installation of the files and all that) always failed because aptitude had somehow screwed it up.

Couldn't find any way whatsoever of repairing the situation, nor would it remove aptitude either because it always crashed, even when using "--force-all" to dpkg.

Result: I had to re-flash my phone to get it working again.