You don't need process explorer. To start and stop services, in Windows press start-run and typ services.msc
In the list you can find the "avast! Antivirus" service and restart it.
Same problem here with avast
4.8-1351.
If I run the web shield (AshServ), it grows in virtual memory hour after hour.
If I stop it, just after my computer starts, it stays at around 30 ko in
virtual memory, but of course it isn't scanning datas from the web...
I don't think this was happening with older versions.
The only way I have
when it becomes too big, is, as you said :
services.msc, then I stop Avast and I restart it.
When done, the virtual memory shrinks from 300 ko (or more) to 30 ko, its normal size.
It avoids to restart the computer each time AshServ becomes very big !
I hope this will stop with a newer version of avast. If not, I'll have to try another antivirus, I guess.