I've upgraded my store to 3.1 and fixed my custom foxybox.css to work with the new version of Thickbox (which I like BTW). The only thing I can't figure out is how to remove the left-double-arrows << or "«" from the continue shopping button. Any help is greatly appreciated.
If you want to see an example of what I'm talking about go to:
http://www.wordfarm.net/books/1602260001/
and click on the "Add to Cart" button. The resulting foxybox shows the unwanted arrows on the "Continue Shopping" button.
Will that work for you? (When in doubt, there's almost always a span around something. We went crazy with spans, divs, IDs, and classes.
It's seriously the best thing since sliced bread. Once you start using it, you'll wonder how on earth you ever did _anything_ before. (Seriously, I'm totally in love with Firebug. If you're a Mac user there's also Xylescope and the Safari Web Inspector (and Drosera, which looks slick but I haven't used it yet), but Firebug is awesome. I can't say enough good things about it.