10
If you are using a windows OS, look in "system32/drivers/etc/" for your "hosts file".
Edit out any adsense entries and see if you have the same issue.
Here's what the legitimate google entries look like:
# [Google Inc]
127.0.0.1 domains.googlesyndication.com #[Parking Service]
127.0.0.1 pagead2.googlesyndication.com #[Google AdWords]
127.0.0.1 adservices.google.com
127.0.0.1 video-stats.video.google.com
# 127.0.0.1 ssl.google-analytics.com #[disabled = Firefox issues]
127.0.0.1
http://www.google-analytics.com #[Google Analytics]
127.0.0.1 4.afs.googleadservices.com
127.0.0.1 feedads.googleadservices.com
127.0.0.1 imageads.googleadservices.com #[Tracking.Cookie]
127.0.0.1 pagead2.googleadservices.com
127.0.0.1 partner.googleadservices.com
127.0.0.1
http://www.googleadservices.com127.0.0.1 apps5.oingo.com #[Microsoft.Typo-Patrol]
127.0.0.1
http://www.appliedsemantics.com127.0.0.1 service.urchin.com #[Urchin Tracking Module]
The more I know, the more I know that I really didn't wanna know.