I've used serout and debug out to run to two different Double-Talk boards at 9600 baud, both performed perfectly, so I'd have to say that you're right, it's probably the interrupts. I tried it using two different LabX-Usb boards, with 18f4550's, with a DEFINE OSC 48. The boards have 20 Mhz crystals, and the oscillator selection is for HS_PLL.

Jerry.