Outlook Express: Strange login behavior

Windows 9x PCs accessing POP server through corporate LAN/T1. Login window randomly appears then hides behind main Window as inbox populates. User has to refocus to the login window or assumes OE is hung. Second scenario: user enters password, then OE does hang (forever) with no error and inbox blank. Started after MSIE 5.5 and 6.0. Random as to PC and frequency??