E-Mails being moved in Outlook

Has anybody ever come across a strange issue where several e-mails in the inbox in outlook 2003 are being ramdonly moved to the deleted items folder….
it usually occurs after work hours and and if the user is left logged in to terminal services it still happens …..
there are no rules setup and the e-mails moved are not from anyone person or are the large either, there totally random…..
the next morning the user just moves the e-mails back to her inbox !!!!