Very interesting point.  I don't experience issues like this when I'm working with Avast on my Windows 7 machine, but I do have a hiccup I can't seem to get rid of.  It can be hard to pinpoint an issue, but sometimes it can take more than a few programs to adequately manage your system and make things more efficient and safe.  

I personally run SpyBot, CCleaner and Avast combined!  

I found this great graphic that covers lots of aspects related to running Windows 7.  I won't post it here because it refers people to a torrent site for a freelegal copy of 7 and I don't want to encourage that, but it suggests using Microsoft's security essentials for protection.  Perhaps the AV system developed in house is up to snuff.  I know I wouldn't have trusted my machine on it before. 

last year i've seen some mistake using avast: after a program update it tell me aboout an intrusion from a local ip on the port 135, it was the ortfor rpc service, and sometime the rpc crashed. I've removed avast was version 4.x but i'd not able o find any inormationon this situation yet. Nowi use security essentials by Microsoft on Windows   7 ultimate and is really light. But i'm still earching for information about avst.

Few weeks after removing avast, I installed Windows essentials. It's light weight, and I find it's good.

The only missing point from avast I miss, is when my PC is sleeping, it cannot turn on automatically. Avast does that :(

Maybe on next release...

Right now I'm using PCTools Spyware Doctor and Registry Mechanic on a brand spanking new Toshiba Laptop U505-S2002.  This machine runs so fast I can hardly keep up.  I love that too.

I had installed Skype and believe it or not, decided not to keep it after all, for two reasons.  My computer ran seconds slower (why was that?) and Skype added icons to all the alt text at over a dozen of my websites.  I HATED that. Uninstalled Skype today. So, am back to the fastest machine I think I've ever had.  

It's surprising how one program can slow things down tremendously. If you are not on top of what happens when you install something new, it can drag you down pretty quickly.

.02

The Skype plugin is something I avoided, but I'm sure you have the option to disable it at well in the settings.  I use Skype daily, so it's a necessary evil for me, sorry it didn't work out for you.  This new version of Skype is awful.  I feel your pain.