This has a lot of options - too many to copy into the body but the accepted answer was:
AVG has been known to cause or aggravate these issues so I would uninstall it and run the AVG Removal Tool to prevent trouble causing remnants from being left behind. Below are recommendations to use while testing, even better permanently.
AVG Removal Tool - run this http://www.avg.com/us-en/utilities
List of anti-malware program cleanup/uninstall tools http://social.answers.microsoft.com/Forums/en-US/msestart/thread/407bf6da-c05d-4546-8788-0aa4c25a1f91/
Here is what I use and recommend : (These are all Free versions and very effective.)
Avast and Prevx have proven extremely reliable and compatible with everything I have thrown at them. Microsoft Security Essentials and Prevx have also proven to be very reliable and compatible. Use MSE and Prevx or Avast and Prevx however not all 3.
Avast Home Free - stop any shields you do not need except leave Standard, Web, and Network running.
Prevx - Home - Free
Windows Firewall
Windows Defender (not needed if using MSE)
IE - Protected Mode
IE 8 - SmartScreen Filter ON (IE 7 Phishing Filter)
I also have IE to always start with InPrivate Filter active if IE 8. (You occasionally have to turn it temporarily off with the little Icon on LEFT of the + bottom right of IE)
Two versions of Avast are available 6.x and 4.8x
Avast 6.x - Home - Free - Stop the Shields you do not use (except File, Web, Network, & Behavior) - double click the Orange Icon in Notification Area - Real Time Shields - click the Shield you want to stop - STOP. To stop the Orange Icon from showing an error indicator - click the Orange Icon - Upper Right - Settings - click Status Bar - uncheck the Shields you disabled - click OK http://www.avast.com/free-antivirus-download
Avast 4.8x - Home - Free - stop any shields you do not need except leave Standard, Web, and Network running. (Double Click Blue icon - details next to OK. - upper left Shields - Terminate those you do not use.) http://www.avast.com/free-antivirus-download#tab4
Or use Microsoft Security Essentials - Free http://www.microsoft.com/Security_Essentials/
Prevx works well along side Avast or MSE
Prevx - Home - Free small, fast, exceptional CLOUD protection, works with other security programs. This is a scanner only, VERY EFFECTIVE, if it finds something come back here or use Google to see how to remove. http://www.prevx.com/ <-- information http://info.prevx.com/downloadcsi.asp <-- download
PCmag - Prevx - Editor'a Choice http://www.pcmag.com/article2/0,2817,2346862,00.asp
Also get Malwarebytes - free - use as scanner only. If you ever suspect malware, and that would be unsual with Avast and Prevx running except for an occasional low level cookie (no big deal), UPDATE it and then run it as a scanner. I have many scanners and they never find anything of note since I started using this setup.