Hello sjm666cn, welcome to the forums.
First, try to repair avast installation.
You can do this from Control-panel -> Add/Remove -> avast.
What is your OS (XP,Vista,7...) and avast's version (latest is 5.0.545)?
If you disable avast, does the problem go away?
If so, try to enable Settings -> Troubleshooting -> "Load avast! services only after loading other system services".
Regards