fuel pump relay

I got the new fuel pump relay for my 560 sel from fastlane and it cured the problem for a while. I drove it once to the gas station, and I ran it a few other times (waiting for paperwork to clear up registration problems), and the last time I ran it, it died and never started back up-fuel pump out again. I jumped out the fp relay and it started up. Do the new relays have reliability problems as well? What now? Thanks,
Chris