Actually, i havent heard many good things about the 2.6.27-9 kernel. If you allow proposed updates in the Sources, you'll be able to upgrade to 2.6.27-10 (the one i have at the moment). This *MIGHT* be the culprit.
to enable proposed packages do this System -> Administration -> Software Sources, enter you password in the gksu box Click the 'Updates' tab, and in the 'Ubuntu Updates' section, its the 3rd option: "Pre-Released Updates (intrepid proposed)." Im sure theres an easier terminal way to do it without typing in vim or gedit too (I think it uses sed and something else), but i dont know how to do it. this is the easiest way i can think of.
Then, run the update manager, and you'll get bombarded with an array of new, pre-released updates (including the new kernel). If you want install them all or just the kernel. When when you're dont, you can either disable the interpid-proposed again, or just keep them (this allows you to be a sort of 'beta tester')
Let us know what happens