I don't think it has anything to do with my audio card, latency, or sample rate, once I get to the mixing part of my workflow it's pretty stable. Let me explain my workflow.
I do backing tracks for my cover band and we normally cover brand new material. In order, this is what I do:
1. Import the original song into X3 and find the tempo.
2. If there is a MIDI available for the song I'll buy it and import it (there are few good places to get them), it saves a lot of time. If not, I transcribe the song by ear.
3. Fix up the MIDI and make sure the parts are correct. I usually do this with my Fantom X6 still using the original GM patches.
4. Find or create the sounds using soft synths, external synths, etc. This usually involves fixing up the MIDI more.
5. Once I'm satisfied with the sounds I bounce everything for mixing and processing.
6. Once the mix is satisfactory I bounce it to dual mono, one channel for the click, the other channel for the backing track mix (minus drums, guitar, and bass).
I normally start with the drums which is when the first crash I experience regularly happens, I like to have the drums as a reference even though I remove them for the final backing track. Usually the drum track has between 5 and 10 different parts depending on the song. Once I'm sure the drum part is close I'll split it so I can mix the drums separately.
To reproduce the bug:
1. Move the original MIDI drum track to the bottom of the track view by dragging it there.
2. Open up the drum track in the Event Viewer and remove all of the MIDI controller data, turn off any MIDI effects, center the MIDI pan pot, and set the fader to 101 and disable it. Remove the hat count in if present.
2. Bounce the modified drum track to clips.
3. Slip edit the beginning and ending of the bounced track to measure boundaries.
4. Clone the drum track.
5. Run CAL Split note to tracks on the cloned drum track, use the cloned track number as the source, the next track number for the first destination track, channel 10, and port 1 (Fantom).
6. Delete the now empty cloned drum track.
7. Go to the end of the original drum track and split all the new tracks there (Split notes always extends a few tracks to the edge of the known universe).
8. Select the tails and delete them.
9. Mute all the tracks in the project
10. For each new drum track:
a. Bounce to clips and adjust the beginning and ending of the clip to measure boundaries.
b. Unmute the track.
c. Audition the clip to figure out what drum it is (this is usually when it crashes)
d. Label the track with the appropriate drum name.
e. If the track is a Hat track merge the open and closed hats by copying and pasting the closed hat track into the open hat track, bounce to clips, and delete the closed hat track.
During the entire MIDI edit process, the only thing that's making any noise whatsoever is my Fantom X (external synth), ALL of the tracks in Sonar are muted except for the one MIDI drum track I'm auditioning. Last night Sonar crashed while auditioning the 7th drum part (crash cymbal) which was the last new track. I haven't tried it, but suspect I could reproduce the crash with no audio tracks loaded. I think I've crashed Sonar at least once for every song I've made a backing track for. I'd be pretty amazed if this has anything to do with my video card, motherboard, sample rate, or latency settings.