Core Data save exception on NSDate
===

I've got this accessDate field, set as date type in the data model. I'm updating the accessDate with `object.accessDate = [NSDate date]` when accessing it.

It is a multithreaded application, and I've done 2 implementations, one with a shared NSManagedObjectContext and appropriate locks, and one with multiple contexts and appropriate merges, both having this exception throwing sporadically.

I've got NSZombieEnabled set in the process environment. I'm a bit out of ideas, so I'd be glad to hear some new suggestions.

The exception is:

    (gdb) po $rax
    -[__NSCFDate longLongValue]: unrecognized selector sent to instance 0x16ddf3020

the object does not look that suspicious:

    (gdb) po 0x16ddf3020
    2012-07-18 18:11:35 +0200
    (gdb) po [0x16ddf3020 class]
    __NSCFDate

and the backtrace:

    (gdb) bt
    #0  0x00007fff8973deea in objc_exception_throw ()
    #1  0x00007fff803bc110 in -[NSObject(NSObject) doesNotRecognizeSelector:] ()
    #2  0x00007fff803348ef in ___forwarding___ ()
    #3  0x00007fff80330a38 in __forwarding_prep_0___ ()
    #4  0x00007fff831ad540 in -[NSSQLiteConnection execute] ()
    #5  0x00007fff831f8e85 in -[NSSQLiteConnection updateRow:] ()
    #6  0x00007fff831f801b in -[NSSQLConnection performAdapterOperation:] ()
    #7  0x00007fff831f7f50 in -[NSSQLConnection performAdapterOperations:] ()
    #8  0x00007fff831f7acb in -[NSSQLCore _performChangesWithAdapterOps:] ()
    #9  0x00007fff831f680b in -[NSSQLCore performChanges] ()
    #10 0x00007fff831f1259 in -[NSSQLCore saveChanges:] ()
    #11 0x00007fff831b4c8b in -[NSSQLCore executeRequest:withContext:] ()
    #12 0x00007fff831b4051 in -[NSPersistentStoreCoordinator(_NSInternalMethods) executeRequest:withContext:] ()
    #13 0x00007fff831e8123 in -[NSManagedObjectContext save:] ()
