Actually, you can stop kernel updates, (unless they've changed it since 8.04)
Just go to System > Administration > Synaptic Package Manager.
Use search to find the name of those updates that are listed in the update manager.
Highlight them (all at once is faster, but separately will work, too), and choose Package > Lock Version on the menu bar.
Voila. You will never be asked again to update those items. Unless, of course, you find them again in Synaptic and unlock them.
Last edited by trlkly; 03-28-2009 at 07:56 PM.
Reason: added unlock info