X2 crashes [inconsistently] when loading soft synths

While testing my Cakewalk synths with X2, I've had several crashes. It happens with TTS-1, GrooveSynth, and sfz. Basically, the synth appears to freeze (no output) while the other synths within X2 work fine. If I then close *any* synth, Sonar crashes ("not responding").

Restarting Sonar fixes the problem, but then it pops up again if I start loading more synths.

Has anyone else noticed this bug?