also, don't concentrate on the jQuery CSS, concentrate on your CSS. where it doesn't happen on a blank page, it is not being caused by the jQuery CSS, it is being caused by your CSS on the page that has the problem.
with fire bug, you can do "destructive troubleshooting". what i mean by this is; in Fire Bug, remove large chunks of the CSS till you find the section causing the problem.
Then refresh the page to load the page again and concentrate on the section you found earlier, removing smaller chunks till l yo find the smaller section, refresh the page and repeat until you can pinpoint the problem selector, then the problem rule in the selector.