I need help with the Outlook error “out of memory or system resources when

THis was working fine for me for months and then suddenly started giving me errors when I try to open encrypted or digitally signed emails form my POP3 server. Looking up the error on the forums, I treid the following: updates for my Outlook nad then unchecking MS Word as email editor, but I am still having the same issue. I have Office PRo 2000 and run on Win XP Pro SP2. Any help will be appreciated. I need to open these emails for my work.

Thanks