Ok, so my .Mac account says :
At this time, Apple is continuing to provide DAT files to current members who have previously downloaded Virex. Please note, Virex 7.2.1 is compatible with Mac OS X v10.4 "Tiger". Virex 7.5.1 is only compatible with Mac OS X version 10.1.5 through 10.3.9.
Huh ???? So only the 'older' 7.2.1 works on Tiger ??
I have the option to download DAT file of 7/27/2005.
No mention of 7.7.
Seems that Virex is not offered any more to .Mac users - but they will continue to offer DAT file updates to existing users.