This has been a ongoing problem since we got this forum (believe we went from pphb or something like that to vbulletin) and there is some weird connection problems between the main site and the forums.
So if you look at the activity thing on the main site it will (for you) say that Toast posted in such and such thread when actually YOU posted something in that thread. It's because you either signed up just before or just after Toast so when she changes her avatar it changes yours (so its her fault). It thinks I'm Seefy.
So it's probably happening because toAst it changing her avatar in the main site and all you can do is go to Forum actions then edit profile then edit avatar and change it on the forum. Forum actions is on the blue bar that is under the tags that say Forum and What's new.