Burning the bootloader is an option, but probably won't result in a fix. In this specific type of case, the problem is really how OSX handles "usb modems". I use quotes since that is what the Uno is emulating.
If you have a ISP you could try re-programming the 8u2. If you can bare to go a few days without a Uno, it might be worth swapping out for another one. However, I don't think you're going to see a difference in another board.