Firefox in Ubuntu 10.04 fouls up display in back-end and front-end

Hi,
I have WP3.01 and have a theme called ‘Midnight Blue (fluid right)’.
I made a few cosmetic alterations and for a week it has been fine.

Today, I played with the admin settings to get a larger editing box, and now i want the two column view back and it stays one column, even though the text box shrinks back.

Also the front end display seems a little out of kilter on just one page. (page not post) and the right sidebar has disappeared.

Strangely, this does not happen with Windows XP and Firefox, but it does happen in my normal working setup using Ubuntu 10.04 and Firefox 3.6, but not in Chromium browser.

Perhaps it is a Firefox issue.
Anyone know of this type of mess up?.

Cheers
Andy