Wow, and that happened after a long 4 weeks? Quite a fighter there the 4850
I thought it was (also) because of unstable or insufficient power supply to the GPU, but I was definitely wrong then. :P
Well, if you're sure that's the only cause, then it's fine. Just for comparison, my friend, who build an internet cafe with HD4200 IGP and Athlon dual core CPU, bought 6 AcBel 420W which one of them died after a year. It just died. So he went to the shop who sold it and got a brand new replacement.
I need to point out that the the warranty is LIFETIME. Which specifically means that if the same model is still in stock, then even after 5 years of usage, it can still be replaced by a new one. I don't know whether or not this is applicable globally, but my point is: if a LIFETIME WARRANTY PSU can die after only a year, how long can a 3 months warranty PSU lasts? Surely it's a matter of luck alone, on how long a no-name PSU lasts.
Unlike other PC parts which varies in features and performance issue, PSU main issue is reliability and stability, especially under heavy load. You won't see an enthusiast PC with "generic" PSU. That's because the builder realized how important a PSU is for a system. Just a little something to think about.
I can tell that you're offended by my comments. That's pride, I know. But you won't be so proud if anything were to happen to that fine rig of yours just because of a $30 PSU. Consider getting an Active PFC, 80+ certified reputable brand PSU which is more reliable.