I upgraded from 7.10 to 8.04 but the process got an error while doing something with pida (upgrading?). Some problem with a file descriptor. I don't have the details because the upgrade window said he was trying to recover and then it totally died before I could copy the errors.
Anyway, I ended-up removing the pida package and do a dpkg --configure -a which got me a few new updates and that was it.
The system is working AFAICS except for the login window which displays only the the top-left quadrant, just enough to see the login box.
So, 1) how can I fix the login screen? and 2) is there a way to check what is missing to finish from the installation process and restart it?