ashserv taken 100% CPU for minutes

Hi, just updated to 4.6.739 and this version is extremly horrible on scanning mails (via thunderbird). Fetching ~50 Mails takes up to 2 minutes, computer isnt usable during this cause avast needs full cpu-power. Using avast for about 2 years without any problems and never noticed something like that. Level high or normal doesnt make any significant difference.

Just an info on CPU Usage
http://forum.avast.com/index.php?topic=16882.msg143240#msg143240