Other users recently have reported very similar problems with Avast 6.x:

http://forum.avast.com/index.php?topic=73054.0
http://forum.avast.com/index.php?topic=72912.0
http://forum.avast.com/index.php?topic=72676.0
http://forum.avast.com/index.php?topic=72355.15
http://forum.avast.com/index.php?topic=70833.0
http://forum.avast.com/index.php?topic=72262.0
http://forum.avast.com/index.php?topic=73159.0 added 3/8/2011
http://forum.avast.com/index.php?topic=74157.0 added 3/19/2011
http://forum.avast.com/index.php?topic=72614.msg620565#msg620565 added 3/29/2011

Here’s a similar problem with Avast 5.1.889:

http://forum.avast.com/index.php?topic=71434.0

The following might also be a similar problem, but it’s not totally clear:

http://forum.avast.com/index.php?topic=72200.15
http://forum.avast.com/index.php?topic=72590.0
http://forum.avast.com/index.php?topic=73276.0 added 3/8/2011
http://forum.avast.com/index.php?topic=74796.0 added 3/27/2011