I would think there is a virus or some type of spy ware on your computer. You should investigate this and take a look at this article: What to do when searches take you to the wrong search website

Thank you, Weather15.

I have cleaned my computer a few times since first noticing it, both with Spybot - Search & Destroy and CCleaner. Also have the latest version of AVG 9.0 Free checking for problems as I search.

I am about to clean again though to see if it makes a difference. Had to do some updating a few days ago and haven't cleaned since then. Thanks again. Will let you know if this handles it!

Fix it !!! I updated Firefox.

I think the knee-jerk response "must be a virus" I've seen here and, more forcefully, elsewhere is probably wrong; there may be a bug in Firefox or an add-on, other browsers don't seem to be affected. I have two virtually identical Firefox setups on different machines (originally copied). I had the jumping problem (type "gimp" in Google search box, click on link to GIMP downloads, jumps back to home page) and was persuaded that it was a virus, so spent the best part of a day hunting (amongst other things booted from Avira, F-Secure, and Kaspersky rootkit & virus CDs, rummaged through logs of "suspect" files which were OK, e.g., Java distribution files, low-level tools like pskill, etc.) and found nothing. I then simply copied the Firefox setup from the good machine to the misbehaving one (backing up and restoring bookmark separately, as the affected machine had the latest bookmarks), and everything is back to normal, so far anyway. I had tried reinstalling the same (7.0.1) version of Firefox without changing settings, but it didn't help. This won't help anyone who doesn't have a backup or extra copy, but it will prevent fixating too much on malware (moderate, but not excessive, paranoia about malware is always good). I would expect a clean install (backing up bookmarks) to be a solution, but a nuisance if lots of plugins to reinstate.