I have a pair I've been running for a year in my PC with no problems. I wanted another 2GB and purchased another pair and my PC failed a memory test (Prime95) in 5 minutes, I took them out and re-ran the test overnight, no problems. I RMA'd them and ordered a second pair.
When the second pair arrived, I installed them alongside the existing memory (with anti-static strap etc. etc. following guidelines) and this time my PC wouldn't even boot. I removed my existing memory units (identical remember) and replaced them with the new ones and my PC went into a start up shut down loop. I put my original memory back in and everything was fine again. 2 batches out of 3 is unacceptable quality control for me. I'm only buying these to match what I already have, otherwise I wouldn't recommend this manufacturer now to anyone.