Similar issue (hope this isn't a hijack): Mine crashes on closing almost every time. Crash report, etc. Doesn't seem to actually hurt anything; no data lost. But it does happen.
I trashed my default preferences and it seemed to help, but have not been able to really "road test" it (I've temporarily brought back the old offending prefs in order to save some of the settings before really throwing them away).
N6.0x 32bit, C4, Halion, UAD-2s, Fireface 800, MC Control, Mac(s) 10.8.x, 16G