Employee Rate Table Records

I did a search on this forum but I didnt find any results on the topic. Is anyone else aware that when you go to Payroll->Periodic Activities->Mass Updates->Rates and change the effective date it wipes out all of the Rates directly from the Employee Rate Table? I happened to be in a training class and ran through it and lost all of the rates in my cronus db. Not an issue for me right now, I still have a good backup of test data. Any ideas?

P.S. Using NAV 4.0 sp2