some obvious things to check would be:
- Driver, on the PC side the ASIO driver is what you want to use, not sure about MACs, though.
- Sample rate, try starting at 44.1kHz, higher settings typically put more strain on the system. Once you have it working correctly there, you can try increasing it if you like.
- Buffer size (most likely culprit) Try starting at 512 then progressively lowering it. Remember that the lower you go the lower the latency (delay) but the more strain on your system resources (CPU mostly).