Out of memory error.

I recently loaded SP4 for Exchange 5.5 on our server. After doing so I am getting “Out of Memory” errors on random Win98 workstations when they send email through Word & Excel or create new journal entries in Outlook98. These machines have from 64K to 128K of memory and nothing else is open, I don’t think it could be a true memory issue.I was told by a consultant that there is a problem with the SP4 but they had no solution for my problem. I have searched the MS Knowledgebase with no luck, asusual. Do you have any ideas? Very frustrated