I noticed that on two Dell Dimension 3000s that I could not select anything during the boot time scan. I had to resort to restarting the computer with a PS2 keyboard. Were there any changes that would have caused this?
I think avast never supported USB keyboards as the drivers for the keyboard couldn be loaded at boot time…
Are you sure you make an USB keyboard work with avast boot time scanning?
The solution is to enable the USB keyboard support somewhere in BIOS (such a setting is usually there).