Outlook Web Access – Help!!

Some Win2K and WinXP clients just started having problems with Outlook Web Access. 2 of the users have CableModem and 1 has an AOL access to the Internet. All can read mail, but when they hit the “Reply” or “Reply All” button, OWA and the entire system freezes up. They’ve cleared cache, temp files, emptied out Recycle bin…still no luck. Mailbox permissions have been verified! Don’t know what else I need to do, pls help!!!