Well I've been thinking about this bug and I think I've isolated the probem a bit and come up with a work-around. The entire problem seems to be with STAR's. So what I did was manually enter the STAR by hand and what do you know, I can use crossing restrictions, change and delete them and change approach and runways. I did multiple revisions and no crash. I know it's a pain to enter the STAR by hand, but it makes the airplane at least flyable until they fix the FMC.

I'd love for others to try this work-around and let me know if it works. So far so good on this end. The only catch is in my test flight I kept a discontinuity between the end of the STAR and the approach. Not too big of a deal really.

Ok. While I was posting this, I tried to close the discontinuity and it crashed. Ugh. I guess if you leave it open between the STAR and approach, you'll be ok. Dunno. Needs more testing.

Please please, CS, fix the FMC.