Hello, I’m new to this forum. I’ve used avast! for three years and just upgraded to internet security 5.0 last month. I’ve never had a problem until last Friday, 2-19-2010. I was online and a windows alert (I have windows vista home premium) warned me that my anti-virus protection was dis-abled. For a few minutes I could not get avast to respond(turn back on) , when it did, everything re-activated except my anti- spam and e-mail protection. It would not turn back on, so I immediately shut down my system and totally unplugged it for 2 days. (prior to shutting everything down I observed my modem lights going crazy) I rebooted everything Sunday and I could not access internet. I isolated system components- with modem only connected to power supply and cable connection, I got same results as when I shut down Friday night(all lights on modem going crazy). With computer isolated from modem connection, it appears it was working properly, I also ran a full system scan without being connected to modem and it came up clean. I conferred with my internet provider (COX-Kansas) tonight and ran through their system checks on my modem and system and they say all is well and don’t know what could have happened. Everything seems to be working normally again, but I am concerned, cause I’m not sure what happened. Could my system be ‘hacked’ or something? Any advice will be much appreciated. ???
Welcome to the forums, horsehead 
Next, you might try malwarebytes antimalware (MBAM) to see what it might find. It is free to use in the on-demand version (free) version. Please download it from the link below, install it, update it, and then run a quick scan. Allow MBAM to fix whatever it finds and post the log here.
http://www.malwarebytes.org/mbam.php