Something is wrong with my AIM. Whenever I receive or send IMs, the IM window appears completely blank. Why?

What I type appears in the little box at the bottom of the window, but when I send the message, it does not show up in the greater portion of the window. It's the same when people IM me. I've tried uninstalling AIM and then reinstalling it, and that seems to remedy the problem temporarily. However, when I turn off my computer and turn it on again, the problem comes back. I have a new Windows Vista machine.. I didn't realize it would be so glitchy. Any suggestions would be amazing.