If you get the following message:

Anti-virus software failed unexpectedly while scanning this file

The following may fix it, but be aware it may not work on all platforms.  I only tested on Windows XP.  After you make changes in registry, reboot computer.  If change doesn’t work, then change back to ‘3’.  I do not have an alternative.

Do not do if you are not familiar or hesitate about accessing the registry.

1. Click on ‘Start’
2. Click on ‘Run’
3. Type ‘regedit’ in text box
4. Go to the following key:
   HKEY_LOCAL_MACHINE >SOFTWARE >Microsoft >Windows >CurrentVersion >Policies >Attachments
5. Double click on “ScanWithAntivirus” registry key and change its value to “1” which is by default “3“.