When running Picasa the first time after installation, set Picasa to view only photos, not videos (Tools > Options > File Types), then quit and re-run. If it works, the problem is your videos. Or use the Folder Manager to remove all but one folder containing ordinary JPG photos but no videos, then quit and re-run. Does it work then? If so, the problem is something in one or more of the removed folders, perhaps one or more corrupted files.