If the Google Toolbar's Popup Blocker doesn't seem to be working, you may want to check your computer for malicious third-party software. This software is often bundled with free programs and can trigger pop-up ads no matter where you're surfing on the web. Please be assured that these programs aren't in any way affiliated with the Google Toolbar, and no third-party software is installed on your machine when you download the Google Toolbar.
If you're interested in learning more about computer applications that embed themselves into your computer without your knowledge (often called "adware" or "spyware"), we suggest reading http://www.doxdesk.com/parasite/
The Google Toolbar's Popup Blocker isn't able to stop pop-up ads generated by these third-party programs. If you think that you have an unwanted application installed on your computer, you'll most likely want to remove the application. You can visit the links above for information on a number of known parasitic programs, including suggestions on how to remove them.
Alternatively, you can download software to detect and remove malicious applications from your computer. We've suggested some well-known applications below. These programs can remove the most common malicious applications, though our users report that you may need to try more than one and having the latest versions is important. Please note that Google has no connection with these companies and can't comment on their effectiveness.
Lavasoft Ad-Aware: http://www.lavasoft.de/support/download/
CWShredder: http://www.spywareinfo.com/~merijn/files/cwshredder.zip
Spybot Search and Destroy: http://www.safer-networking.org/en/index.html