I have the solution. I called the support and they said that the new USB drivers on the new mac's are not configured to work perfectly with the scarlet interfaces. So he send me a download link and instructions. I'm so happy this worked. Here is his email back to me, hope it helps you!
"Thanks for your call and sorry to learn of the problems you are having with your Focusrite product.
Some users have reported experiencing audio glitches and drop outs with the Scarlett range of interfaces since updating to OSX 10.9 Mavericks. If you are experiencing these problems with your interface, it is possible to utilise Apple’s USB audio driver by downloading and running the class compliant mode application below, while we investigate further.
Please note: After the class compliant mode application has been unzipped, please right click on the application and choose "Open". If you do not do this you may get an error message from the Apple Gatekeeper service
Please feel free to call us back on +44 1494 462246"