Bug#479130: Could not calculate the upgrade

[Matt Kraai]

Package: update-manager
Version: 0.68.debian-3

When I run Update Manager, it displays a dialog that contains the
following text:

 Could not calculate the upgrade

 A unresolvable problem occurred while calculating the upgrade.

 Please report this bug against the 'update-manager' package and
 include the following error message:
 'E:Error, pkgProblemResolver::Resolve generated breaks, this may be
 caused by held packages.'

I don't know how to check whether I have any held packages.

-- 
Matt