I just upgraded my xubuntu 11.10 to 12.04 and now, when I login into the GUI, I have to wait about 3 minutes before the desktop appears. Only the background image is displayed. 
The login into the console works fine (with ctrl+alt+f2)

Even stranger: 
If I login first in the console and then in the GUI, it boots quickly. 
 If I login first in the GUI, switch to console and login, it takes 3 minutes to boot in the GUI.

My machine is a thinkpad T420s.