I used to run Trend Micro Antivirus with Webroot Spyseeper and they ran fine together until one day after I updated the Spysweeper definitions my system just locked up. Long story short, there was something in that update that made them no longer compatible. I don't know if that's what's causing your problem, but there could be remnants of AVG hanging around that were okay until the latest Avast update. As far as getting AVG completely off your system, a removal tool is probably better than Add/Remove Programs, but I've found them to also be ineffective in some cases. Here's how I do it when all else fails.
First uninstall with Add/Remove Programs. Then go to My Computer>Drive C>Program Files (or wherever it is, usually here)>Find the program folder and delete it.
Next search the entire system for files and folders that might be associated with the program. You'll have to be careful here if you have more than one program by the same manufacturer. You only want to delete the files associated with the program you're trying to remove. Some files may not delete at this stage because they're registry entries. Just delete the ones that will.
After that I clean my registry with
CCleaner and/or
TweakNow. I've been using both of these for awhile now and never had any problems with either one. Just make sure you know what you're doing before you use them.
When you're done with the registry, reboot and search your system again. This time all the files you want gone should be gone. If not you should at least be able to delete them now.
This is a pain in the a** but so far it's worked very good for me every time I've tried it.
