When attempting to auth against a mongod with kerberos, the driver makes a call to unmanaged code which (according to WinDbg) causes Heap Corruption, which, in turn, brings down the CLR. This type of crash cannot be caught. Previous versions of the driver do not appear to have this problem.
I have traced the problem to MongoDB.Driver.Communication.Security.Mechanisms.Sspi.SecurityContext.GetMaxTokenSize(), Line 418.
The faulting module shown in the crash dumps is ntdll.dll.