Its not a 1.5 thing so it must be one of your extensions, tell us what you have on it and then we can probably either find out which one to disable or get you started on testing the most likely ones.
Should be a simple job to test, find an online form, set it as your homepage. Then you just disable the extensions one by one until it stops doing the tab thing, then you just remove the one that does it or just leave it disabled.
Disabling is just done by right clicking and selecting disable on the extensions menu.
Easy as pie, you will have to restart firefox each time you disable an extension for it to come into effect before you test it.
So you dont have to uninstall them at all.
Edited by warriorscot, 08 December 2005 - 04:19 PM.