Today, on my client's computer, I got about 20 events in the Vista Event Log saying 'A timeout (300000m/s) was reached while waiting for a transaction response from the avg8wd service'.
What does this message mean?
It is AVG Free 8.5
Windows Vista Premium SP1 32-bit
Spybot S and D 1.6.2
ZA 8.5

Sounds like it was trying to update and has kept failing

You may know my standing on AVG and that is to remove it, anyway here's the best advice you'll get

Uninstall your AVG Antivirus
Then run the removal tool
Here is the 32Bit version (most users): http://www.avg.com/filedir/util/avg_...avgremover.exe
Here is the 64Bit version: http://www.avg.com/filedir/util/avg_...removerx64.exe

Restart

Install Avira free AntiVirus

Update it

Run a full scan, and remove all the Viruses that AVG missed

The wd in avg8wd means WatchDog.

If the service problem is caused by lack of communication, this can be due to the firewall blocking it, website busy, corrupt file, malware, insufficient user rights etc.

If your client must stay with AVG, try uninstalling and re-installing it to repair the files, while making sure it gets full access rights from the firewall. A previous on-line malware scan wouldn’t hurt.

Better still, of course, is to follow kimsland’s advice, which not only has a better chance of working but will also leave your client with a better AV.