My problem began when I was mass mailing my newsletter. Seems that one, or more addresses were corrupt. The problem is not with the newsletter, as I was sending it a batch at a time.
More info: This is what the 'Problem Details' says:
Application Specific Information:
*** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '+[NSCFSet isTemporaryID]: unrecognized selector sent to class 0x1024fd038'
ha...I found the answered to my own problem...let's hope.
Retrieving data ...