You could download the 66??xdat.exe file and apply it to that computer to get it up to date. Hopefully, once updated, it will have an easier time with the incrementals.
As Andy mentioned you can install the xdat from here manually: https://secure.mcafee.com/apps/downloads/security-updates/security-updates.aspx? region=us
But both of these products are EOL and pose a great security risk.
As sometimes this can be caused by McAfee Agent then you could try to upgrade to latest version of McAfee Agent 4.o patch 4 (184.108.40.2062) that was made only for Windows 2000 SP4
Thanks guys.after copying the dat files manually accross, and a process of re-installing the AV as I noticed the service for mcshield was a bit flaky, it resolved the issue.
I have another question in line with this though.
will the update task attempt to download the full zip file if it fails on incremental or can this be prevented and later initiate manual intervention
I've had a similar issue
I can up with two solutions
1. Set a time-out on the update task. If the link is so slow and the zip download exceeds the time then the update is cancelled.
2. Set up a repository local to this particular desktop that is replicated out of hours. The repository only needs to contain the DATs. If the desktop fails it's GEM updates it downloads the zip file locally and doesn't impact on the network
Also answering your last question in your original posting, I have worked out a process of manaully rolling back the DAT when this happens
Note: with the right tools this can be done completely remotely
1. Stop the Access Protection process
2. Stop the 'McAfee FrameWork Service' and the 'McAfee McShield' services
3. Navigate to "C:\Program Files\Common Files\McAfee\Engine\OldEngine" and copy the 3 .dat files in there to the previous directory "C:\Program Files\Common Files\McAfee\Engine"
4. Restart the two services stopped in step 2
5. Start the Access Protection process
6. Retry the update
9 times out of 10 this will fix the issue
If this machine is failing it's GEM updates on a regular basis then one thing to do is check the RAM on the machine. Run a memory test (something like http://www.memtest.org/)
I had a machine that due to a faulty ram stick would fail it's updates. Probably something to do with the checksum calculations McAfee would do to validate the update files. With the faulty ram these checksum calculations wouldn't match and therefore the update would fail.