I set up a test case for this here: http://www.virtualergonomist.com/jquerytest.html.

jQuery is causing tables with border-collapse: collapse, to lose their borders in FireFox 3 (3.0.9).

We have one main stylesheet that has our reset and global styles. In that we define table { border-collapse: collapse; }. We include this stylesheet, then jquery. After that we will include any view includes, in this case another stylesheet that defines the styles for a table with borders. In FF3 the borders disappear after jQuery initializes. In all other browsers the borders remain. Take jQuery out, the borders are back in FF3.

What's interesting is that if I define the table styles inline, the borders remain, or if I move the stylesheet that defines the table styles above where jQuery is included the borders remain.

This is easily worked around, but bizarre nonetheless.