Can’t delete email dated 12/31/1969

A user has 2 blank emails showing up in her Netscape email. The date of the email is 12/31/1969 with no address, IP or message source. When both are deleted, she clicks on the trash folder and only one appears. Once deleted she goes back to the Inbox and both messages are there again. Closing Netscape email doesn’t work either. Once it’s reopened the emails are there again. Running WinXP SP2 home edition & Netscape 7.1. Spybot, Ad-aware & CWShredder show no virus. Any ideas?