overclocking troubles

[Film]

okay ive had my 1800+ tbred-a for a short while now... and running into problems.

ever since i got it i have been running it at 1975mhz w/ 1.85vcore totally stable. all was well until about a week ago all of a sudden i started getting lockups, bluescreens, other misc queer stuff. so in return i had to back down the overclock. being lazy i knocked it down a bit a didnt bother to see how high i could go stable then. regardless i ran it at about 1850 or so for about a week when i finally got off my ass and got what i needed for a voltmod to my kx7-333r.

so i get the stuff and i have successfully moded my board... i bootup with a nice 2.05vcore first and see what happens... i cant even boot 166x12.5(2075), i can pretty much do exactly what i could before with 1.85. so i knock it down to 1.95vcore and started burning in and i am currently stable at 166x12(1996) -- bumped it up 1 fsb for 2008mhz and it locked up!

so you see my problem, my once DECENT oc chip has begun to fail. i use custom watercooling (though not great it gets it done), and my voltages seem to be fine. what could cause something like this and why is everyone BUT me getting much higher overclocks out of their 1800+ tbred *note: my stepping posted at bottom* anything you guys can think of, ill try. if all else fails i guess ill buy a new 1700+ tbred-b

stepping
AXDA1800DLT3C
AIUGA 0249SPDW
9513777260015

[Tweaked!]

Film, Welcome to Xtreme!

I wouldn't exactly be so quick to think that the chip is degrading yet. For one, what are your temps, both ways, water cooling and air? At 166fsb, have you lowered or locked your agp/pci? Have you tried lowering your ram timings?
How about giving us a full spec layout. Let us know what we're dealing with here.