How can I prevent the Google+ app from showing the wrong thumbnail before I share a photo?
Ok, I think this might be helping, but it's an odd fix. . .

After reading the answer to another question on this site I tried the following:


Settings | Applications | Manage Applications | All | Media Storage | Clear Data
rebooted phone
opened Gallery app (nothing there, but I should have seen one picture)
took a picture (now pictures started appearing in the Gallery app)


And now the Google+ app shows the correct thumbnail. . . for now at least.  This is a pretty serious kludge and not at all user-friendly.  I hope it helps someone.