It looks like the muddled kernel packages are still an issue. If you haven’t updated yet, don’t. The developers have been aware of the problem for a while and have promised a fix ASAP. A bug report is here.
If you managed to somehow come up with a completely borked system, you might try to specify an earlier version for a downgrade. The apt-get install tool has a provision for selecting an exact package:
A specific version of a package can be selected for installation by following the package name with an equals and the version of the package to select. This will cause that version to be located and selected for install. Alternatively a specific distribution can be selected by following the package name with a slash and the version of the distribution or the Archive name (stable, testing, unstable).
Check your man pages if you need more information, or if you need to try a downgrade to get your box working again.
I’m not going to post the downgrade command since I don’t have a means to test it, and I don’t want to give an incorrect command. If your system is still functional, but not upgradeable, stand your ground. If it’s not functional and you’re willing to risk it, construct the command on your own and keep your fingers crossed. 😉
Edit: Don’t forget that the problem lies within the security repositories, so I believe disabling those with Synaptic or through your sources.list will allow you to upgrade other software without trouble. Remember to re-enable them when the fuss clears.
Edit: And relax, people. Don’t get wound up over this. This is nothing compared to the X server catastrophe back in August. 😀
Motho ke motho ka botho 