Well, I've got a 14K50 here now, and it enumerates and holds the USB just fine.
So far I haven't got a single blink out of RC3 yet though.

Not sure what's going on there, but I'll play with it some more tomorrow.

I'll add some USBIN/USBOUT statements too and make sure CDC is really working.

What operating system are you using?
Win7-64 here.