Sorry, I don't have Net access right now (I only get 10-hours a month, which is just the way I like it) and I'm using my sister's box across town. Anyhow, I hadn't noticed that you replied back to this.
Yeah, I don't know squat about midi. I have to think that you can get much better performance than you're getting though. I wonder if it might have to do with what you're using for the timing master? I'm not sure how that works with midi. Boy, I'm lost with midi stuff. Have you tried asking guys in the Sonar forum. There are quite a few who use midi there. They'll probably give you a hard time about using an SB card

but try to patiently ignore that end of the conversation and maybe one of them that has used an SB in the past can tell you how to fix things. Besides, I think a lot of guys are still using their SB cards in conjunction with a second one for regular analog use. Some guys like using the SB for the synth stuff.
Sorry, I'm out of my frame of reference with this one. I'm sure there's a way to get better performance though.