While I stand by my glowing review of Xubuntu 6.10 (Edgy Eft), I have yet to find any release of any Linux distribution which was free of bugs or quirky behavior. The latest releases of the Ubuntu family of distributions are no different.
One of the nice things about Xfce4 is that it is very easy to customize and reconfigure any way you like. However, if you go into Settings -> User Interface Preferences to change around your desktop theme be careful about then also changing your icon theme. Some work, some don’t. Changing the theme to either default or Grounation crashes Xfce. It won’t start again, either. The fix is to restore your .config directory from backup.