My clients problems were errors and application crashes (lacert Tax and a VB/MS Access based payroll program), data write failers and corrupted MDB files along with slowdowns. Setting things to normal only fixed some problems. However, I beleive I've found the fix. I turned off the scan created/modified files under Standard shield -> Scanner (advanced). This stopped the remaining crashes (so far). Since I could not edit the default list of extentions to remove MDB I just disabled this setting and all is well again.
I left the "Scan files on open" option checked but I have not added any extenstions to the list.
Aside from the crashes, things are running much faster for their apps, faster then this morning. As long as the crashes go away, they will be happy and I can keep evaluating Avast.