Glitchy progress bar during full system scan

I came across a weird problem while running the full system scan today. The progress bar doesn’t seem to be working correctly. The first time, the progress bar shot to 100% within 4 minutes of the scan and kept scanning (it usually takes ~1 hour for the scan to complete). I stopped it and ran it again, this time the progress bar was stuck at 2% even about 30 minutes into the scan. I restarted the computer to see if that would help, but the problem kept occuring. Within minutes of each scan, the progress bar would just go to 50%, 100%, whatever.

If it helps, I’m using program version 5.0.462 and database version 100402-1.

There is same issue here:
http://forum.avast.com/index.php?topic=57986.0

I think progress bar glitch isn’t urgent problem (the mission of anti-virus software is protect our PC from viruses ;)), but if fixed, it’s much better.