if it failed once (when you had to run diskwarrior on it) and you're still experiencing problems, you're probably still seeing the effects of whatever problem it had in the first place. you might want to run some more hardware diagnostics on it to see if you can turn up any problems.
also, i would try changing the startup disk to your 2nd drive and starting from a clean powerup. if you get the same problem as before, it might indicate a hardware or power problem. if it boots fine, you're probably seeing a software/OS problem.
if it's a hardware thing, try running your 2nd HD in another mac to see if it's actually the drive, or a bad connection somewhere. but like i said; if this drive failed in the past, it might be connected to that.