This is the same issue as in this post:
That thread had been makred Resolved, even though it wasn't, so I am opening a new thread in the hopes that the plugin author will see it and attend to it in the next version.
The problem was with line 49 in includes/wpsr-retweet.php. The plugin was stripping out all ampersands (&) and pound signs (#), so this:
was becoming this:
I modified the str_repolace to not remove those two characters and it started working again. I am not sure why he was doing that in the first place, but it was definitely deliberate so in some cases this fix may break something else. I am only using the Twitter button, and the same function pertained to both Tweetmeme and Topsy, so it's possible those won't work with these changes.