How to fix a hanging Logic Pro 9.1.5 on Snow Leopard?
I looked at your hang log (also called a sample). I have some experience reading samples for Mac OS X apps, and with Logic Pro 8. Unfortunately, I can't determine the problem from your log file. 

If this problem is fully reproducible, it sounds like a bug. There may be nothing you can do aside from work on a different project or a new project within Logic. If you haven't already, report this to Apple via http://bugreport.apple.com/ .