Problem with updating

[Petko]

  Hey guys , I haven't updated for the last 2-3 days and now as I 
decided to do it the update manager tells me that a partial update must 
be made first and then the whole thing . So ok , I go ahead , but as the 
update dialog shows (same as the one for updating to the next distro 
release ) on calculating changes it tells me that I don't have the 
ubuntu-desktop package (which I checked and do have (also reinstalled in 
synaptic to be sure) ) . So has anyone else encountered that or know how 
to fix it ? (I'm on Precise if it hasn't become clear )

Petko