You can try taking the radio out and the faceplate off, then clean the button membranes/switches. I know taking out the radio is much more of a pain in the Sky than the Solstice - you'll have to search taking the dash apart for that. But ater that, taking the faceplate off and apart is not too bad. See pics:
(9) I need a dash removal DIY [project now finished - painted dash] | Page 2 | Pontiac Solstice Forum
(9) Migrated my (old) Solstice Radio faceplate to my (new) Sky USB radio! | Pontiac Solstice Forum
(9) I need a dash removal DIY [project now finished - painted dash] | Page 2 | Pontiac Solstice Forum
(9) Migrated my (old) Solstice Radio faceplate to my (new) Sky USB radio! | Pontiac Solstice Forum