If you are running McAfee Security suite, a recent update may be causing this problem. See the following post:

http://forums.us.dell.com/supportforums/board/message?board.id=sw_winxp&message.id=159216

Steve

Right click IE on the desktop, select properties. On the General tab, delete cookies, temporary files and history. On Advance tab, click on Restore Defaults button. Apply and OK. If this doesn't work, you can see if this Microsoft Support helps.