I assume you're using VS 8, but..
Whenever posting questions on these forums, please give us as much information as possible about your computer. We need the operating system, processor speed, amount of RAM installed, brand name of the computer, (if there is one), and any EXACT error messages you are receiving, and the EXACT version of Virus Scan, plus the scan engine and virus defintions that you have installed. (RIGHT click on the McAfee shield, or red "M", in the lower right corner, choose "About Virus Scan".) The more information you give us, the better informed our answer will be.
In the meantime, the only thing that has been available for your problem is a "work around". First, if you happen to have the ability to view the e-mail from a webmail account, you can delete the offending message first, then download the rest of the messages to your Outlook Express and things should work fine.
This is the generally accepted workaround:
Press Ctrl-Alt-Delete, to bring up the "Task Manager". Click on the "Processes" tab,(if using Win2000 or XP), or look for a process called "McVSEscn.exe". Highlight it by clicking on it once, then click on the "End Process" button. ("End Task" if using Win98/ME) (This temporarily disables the e-mail scanning.) You can now download the e-mail. After downloading to Outlook Express, then RIGHT click on the "M" in the lower right, choose "Virus Scan", then "Disable". Now RIGHT click on the "M" again, choose "Enable".
Remember, since you disabled the scanner temporarily, make sure to manually scan each message. Here's a link on how to do that:
http://forums.mcafeehelp.com/viewtopic.php?t=9082