Not that I wanted to bump this thread to the top, but I saw it and thought I'd respond.
AdBrite doesn't do any type of browser hijacking. We also don't do popups, direct links (SEO spam), or anything else sketchy. In fact, we didn't even set cookies until recently, when we couldn't figure out any other way to do conversion tracking (code that shows advertisers which of their ads are converting into actual sales).
Most likely your site is having a problem with our Interstitial/Intermission code. Interstitials are full-screen ads with a big "Skip this ad" link on the upper-right.
We have heard on occasion of these ads sometimes performing weirdly on sites with lots of other JavaScript/CSS/DHTML stuff going on. If that is the case, you can go into your AdBrite account and turn off Interstitials. Also it would be helpful if you could send us your URL, so we can debug. We'll send you a free tshirt or something for your troubles. Consider it hush money.
Sorry for any inconvenience. Everyone should be aware that Interstitials are (and always have been) by default OFF for all publishers. If a publisher is interested in these types of ads for his site (starts at $5 cpm! okay there's my plug), he must manually turn this option on himself.
Thanks for reading,
pud
www.adbrite.com