AVG Free Edition has a considerably lower malware detection rate than AVG AntiMalware (due to the lack of the Ewido Scanning Engine).
A quick test to make sure that this is not being caused by adware / viruses / malware would be to:
1. Download and install
SuperAntiSpyware (install and update it, do not start scanning yet)
2.
Install the Kaspersky Browser Based malware scanner (let it install the activeX control and update, do not scan just yet).
3. Restart into
Safe Mode with Networking (make sure Windows Firewall is on or that you are behind a router or have a firewall solution of your own)
4. Run a deep scan with SuperAntiSpyware
5. Run a scan of local hard drives with the Kaspersky web based malware scanner
6. If Kaspersky finds malware that AVG missed, you can get the
AOL AVS for free that uses the Kaspersky engine to remove it, Kaspersky's online scanner does not remove the malware, only detects it, but the AOL AVS will do both or if you prefer, you install the trial version of Kaspersky which has some added features.
7. If these adds do not originate from Adware, install
FireFox and an addon for it called
addblock Plus, which has a subscription list of continually updated known advertisements that it automatically blocks. Migrate to it as your primary web browser to get these features.