It's a long story and not completely the integrator's fault but in the end we had to replace all of the memory. Since then we have stuck to the same part manufacturers where possible. We don't know whether we've just been lucky or simply haven't reached a critical mass where it becomes a common problem, but it's been extremely rare for a part to arrive in working order and go on to fail within the warranty period. Maybe that's a testament to Supermicro, we have had some problems with their power supplies but all sometime after the warranty period has ended.