Ian,
Thanks for letting us know. We see that you have an ABV378PRO board model. For this model board, and your Mavericks OS, you will need to use our latest driver. We will include a link for you to download it here for your computer:
promethean.box.com/.../1l5cb7hvwqj041x5ho6i
Please use that link to download the latest driver for your system. Disconnect Promethean Hardware from the computer, and then remove the old driver. Once that is removed, please install this new driver, and then reconnect your board's USB cable to the computer. Then test again, and let us know if your issue is any better. Just reply here with your results, or you can also call us with your case number.
Let us know if you have any questions.
Thank you,