I have McAfee security running and recently it has been notifying me that a file is trying to send email. This has happened a number of time and the files are located in the Windows\System32 directory and several run entries get added to my startup. I delete these and move the file to a tmep directory and something seems to change the file name and start the process all over again. Here are the file names that have showed up:
bjehvuw.exe
eb.exe
nemloi.exe
tbvtnvgdq.exe
yjyssqllbzz.exe

Any idea what is causing this and if it could be a worm or virus?

First try all your basic up-dated Spyware scans
Spybot S&D
Spyware Blaster
Adaware SE
and a free online scan with x-cleaner http://www.spywareinfo.com/xscan.php

Then try some on-line scans with Housecall and Kaspersky as they will allow you to remove the infections.
Post back your results. Good Luck

Hopefully my advice will help you...Please post back with your results....thanks