Unless something has changed recently with the restrictions (which is quite possible), I don't think the forum will allow you to upload a profile picture that is too large in file size (especially since it is for a small thumbnail sized picture). Try knocking down the image to something smaller. I first tried to do this with the raw image from my digital camera, and it did not work either. When I made it smaller it worked. If you are unable to size it correctly, Email it to me and I would be happy to do it for you.
Adz28@wwwebtek.com