While some greases may be incompatible, 10:1 or higher that it wasn't your problem (assuming they were both high temp wheel greases). See:

http://www.mindconnection.com/library/handyman/greasecompat.htm

and

http://www.noria.com/message_boards/message_details_by_list.asp?foldername=mixing+incompatible+greases&messagenumber=4787

As to the nuke plant operator, we know they had to fail on the safe side regardless of the real risks, once the consultant hath spoken. Why didn't you just recommend cleaning or flushing of the grease?:wtf: Now the consumer has to fork out the millions in higher electric costs.