I don't know if I should configure JACK differently or what, but I can only work on a session for a few minutes before the vocals start playing back late to the piano. I can't figure out if it has anything to do with the latency I'm running or my buffer sizes (I don't really understand buffers, so I'm not sure how it could contribute or if it could). I've been running the highest latency possible, since I'm done tracking and am into mixing now. If I restart the program it typically (not always) fixes it, but it will just recur a few moments later with varying degrees of awfulness. I'm running Ardour 2.8.11 on an iMac with a 3.06 GHz dual core processor on OS X 10.6.5. I have done a few other sessions since installing with excellent results. I have only noticed the problem on one session, however that is the only session I have been working extensively on, so I can't be sure whether the problem is universal or not.
One thing that is interesting is the piano was tracked in stereo, but when I brought the session into Ardour I brought it in as two mono piano tracks, and they never get off from each other.
I know I might be leaving out some important information that might help you guys understand the problem better, but I wouldn't know what to post. Any ideas?