Comment 48 for bug 996791

I had the same issue with Xubuntu 12.10. Suddenly after adding some applications and updates, I notice a slow login. I got a black or grey screen for some 20 seconds before the desktop showed up. Once the desktop appeared and say a terminal window was launched, it took about a minute for it to pop up and be useful.
For my configuration, removing the XFCE config file resolved the issue.
I followed the instructions given somewhere here or in another forum :
1) Ctrl-Alt-F2 to get out of X onto a command line
2) login there
3) sudo rm -rf ~/.cache
4) sudo rm -rf ~/.config/xfce4 ## this kills your desktop setup, i.e. background picture !
5) Ctrl-Alt-F7 to get back into X
6) reboot

Credits to the author of post, I can't find anymore! :-)