Full system scan decreases in speed - Avast 5.0

[Hardwired]

Hey guys.

I've been having some issues with the full system scan on Avast 5.0.

When I start off the scan it is quick and effective. But it starts to slow down in how many mb/s it scans. After about 5 minutes im down to 40 mb/s, after 15 minutes we are on roughly 15 mb/s. This is in my mind not normal behavior.
I have tried to restart and looked through the settings with minimal success.

I am running Windows 7 64-bit.

Suggestions?

[silviucc]

Could you  post you system specs and also tell us what OS you are running ? Since you mentioned a 64bit OS I presume Vista or Win 7. Any other "security" software running ?