I updated from Bitdefender 2009->2011, and when I launched the installer it had me uninstall 2009 like it should, but then it asked me to restart the PC so I did. However someone else logged in a non-administrator account after the restart, and Bitdefender's installer (which automatically started up to complete the installation) acted weird, not showing many of the graphical buttons. So I uninstalled it, re-booted, and installed it, and now it works great.
If the installer would check to see if it was an administrative account I think it would solve the issue.
running: XP SP2
