computer locks up when disconnecting fro

I have an amd Athlon 650 mhz with 256 mb memory and 20 gb hd when i disconnect from AOl and they attempt to update AOl the computer either freezes or the screen goes blank i have reinstalled the software, downggraded to aol 4.0 and still have the problem i have changed to external and different external modems and the problem persists. I have closed all running programs except explorer and systray still no luck. This has been a problem ever since i purchased the computer. I ran freewwweb and didnt have any problems. I cannot get any intelligent answer out of AOL. I was hoping that some one else may have run into a similar problem. I also deleted the TOD file and reinstalled it250