Try taking a combination that didn't work in a bus and try it in an Aux track or an audio track.
I'd try it myself but even using Channel Tools and Boost 11, I'm not able to duplicate.
Another thought: What happens if you double the latency (e.g., 128 to 256 samples)? I'm not saying that's the problem, but it could give a clue from a diagnostic standpoint.
Also, I assume you're not using ASIO4ALL...right?