This sounds like a case for the Support Team! Sidenote, in 6.8.4+ there have been measures put in place to prevent AV update failures in the form of a more robust update procedure and additional countermeasures.
did your webwasher get his update?
our webwasher had the same issue.
In the error.log there was the following entry:
[26/May/2010:12:29:24 +0200] Exception \'Cannot allocate memory\' when decompressing archives in AV Update
Did you have a look in the error.log? After an restart of the webwasher-csm the update works fine.
the problem is solved according to another post in the community:
1. Stop WebWasher-csm service
2. delete folders in /conf/antivirus
3. restart Webwasher-csm service
Once done the software will immediately retrieve new updates.
Thanks for the help.