Update 10.04 -> 10.10: pkgProblemResolver::Resolve

[Paolo]

Binary package hint: apt

Description: Ubuntu 10.04.2 LTS
Release: 10.04

Synaptic package manager: 0.63.1ubuntu14

Trying to update from 10.04 to 10.10 release:

Message box appears with message:
An unresolvable problem occurred while calculating the upgrade:
E:Errore, pkgProblemResolver::Resolve ha generato delle interruzioni. Questo potrebbe essere causato da pacchetti bloccati.

[Translated]:
E:Error, pkgProblemResolver::Resolve generated breaks. This could be caused by blocked packages.

Only available button is "Close"
A white cross in a red circle appears on the left of "new channels" in update dialog box.
System is restored to original status. ["ripristino dello stato originale del sistema']

I expected update to work up to the end of the process without error messages