Alright, let's start simple.

Go here:

http://daol.aol.com/software/aoldesktop96/

Download and install the AOL desktop software, and choose Upgrade during the installation procedure.

If that doesn't work, attempt a system restore to when it was working. To do this, go to start, all programs, accessories, system tools, System Restore.

Choose more installed dates. Choose a date prior to this issue occuring.

Once finished, to return to me, go to www.justanswer.com and click my questions.

And last but not least, if that all fails. Clear your startup to see if there's a conflicting program. Start > run. Type msconfig and hit enter. Click the services tab, click Hide Microsoft Services, then click Disable ALl on the right. Restart. You may enable one service at a top to determine the cause if this resolves the problem by going back to that field, clicking hide microsoft services, and checking which items you'd like to reenable on startup.