My lenovo thinkpad has keys above the left and right arrow keys, that by default are wired to my browser's "forward" and "back" buttons. This is a horrible idea, because it means that frequently I'll accidently hit them while entering text in a textbox, and lose all my edits when the browser leaves the page.
This fixed it for Ubuntu Lucid (running gnome):
System ... Keyboard Shortcuts ... Add ... Name: Do nothing ... Command: /bin/true ... Apply ... click in the "Shortcut" column for the newly created shortcut ... press the browser back button.
It should display as "XF86Back". Now repeat, creating another shortcut for XF86Forward. Problem solved!