I'm another Dell user with Win 7 64bit and Avast 4.8, I have the same problem, here's a copy of the posts to http://social.answers.microsoft.com/Forums/en-US/w7files/thread/08118bac-3ef1-4208-8192-d8252d7cc660
When I first start Control Panel, the Control Panel windows says "not responding", I then get the Windows dialog asking to restart the app etc. After the Explorer restart I can access the Control Panel functions without a problem (thankfully). This problem is 100% repeatable after logging in.
The Windows Event Log details are as follows:
The program Explorer.EXE version 6.1.7600.16404 stopped interacting with Windows and was closed. To see if more information about the problem is available, check the problem history in the Action Center control panel.
Process ID: ae0
Start Time: 01ca99bb77a8fa90
Termination Time: 0
Application Path: C:\Windows\Explorer.EXE
Report Id: 619fe1b6-05dc-11df-b48f-0024e8f2bcb4
The problem only happens after a restart, not if I restart Explorer then logout and login. I used the Win 7 Clean Boot procedure (msconfig utility) to track it down to the Startup item Avast ALWIL. ie. disable the startup of this item and the problem goes away. This suggests its a problem with Avast 4.8