I have not encountered a problem with X2a until now. I can instantiate Korg Legacy Cell in projects and can work with it in X2a, but when I save a project that uses Legacy Cell, X2A locks up, and I have to close X2a via the task manager. I know that Legacy Cell has had a spotty past with Sonar, but is there a way around this problem?

It probably only works in 32-bit so install and run the 32-bit version of Sonar.

Is it the latest Legacy Cell? Either way that synth no likey Bit Bridge if you're using it in the 64 bit version of SONAR. I switched to jBridge and it behaves nicely for me now. I was using it yesterday without a hitch. Korg is promising 64 bit versions this year, possibly in the spring for all the legacy stuff. I will welcome that (if an when it happens) with open arms!

Much to my surprise, I did not have jBridge enabled for Legacy Cell. I enabled it, and Legacy Cell works now. Thanks all.