shutdown changes ubuntu to Xubuntu?

[David Armour]

hello list,

this morning when i restarted my computer, the desktop had changed from 
ubuntu to xubuntu. i've used xfce in the past, but it wasn't on the 
screen last night when i shutdown. sono perplesso! (i am perplexed.)

i logged in as the same user, same password. and i have no idea how to 
reinstate the ubuntu desktop. already tried re-starting, and well, this 
is coming atya via thunderbird and xfce.

any response greatly appreciated.