Dead RAM?

Specs
MOBO: Gigabyte P35-DS3L
CPU: C2D E4500
MEM: 2 gigs OCZ 6400
GPU: Nvidia 8800 GT
PSU: TruePower Trio (550, I think)

I built my own system hassle free in January, but there has been one little issue that crops up now and again. When I play graphically intensive games, I get more lock ups and IRQL_LESS_THANs than I ought to. I know this is usually a driver issue, but I think I may have finally found the problem in bad RAM.

My OCZ 6400 isn't passing muster with Memtest. I haven't been able to get a full run through. It just freezes (but not always at the same place). That means it's bum RAM, right? Anything else I should try to fix the IRQL errors?

My question is, do you think it's worth the hassle to RMA the stuff (lifetime warrany) or just buy some new RAM? I think otherwise the system is sound. (Full specs when I get home). The FPS is in the right range when I play Oblivion and Witcher, but they're both nigh unplayable with the frequent crashing. The computer never crashes when running other desktop applications (except Picasa 3, once).

If I should buy new RAM--what should I get? This stuff wasn't rated poorly on Newegg (I picked it up at Fry's).

I'm not overclocking anything.

I'd like to have a playable system for Fallout 3 come Christmas time when I'll have a break from work. Thanks for any advice!

Updates in bold. Anyone RMA'd stuff to OCZ before? Advice?

Yep, good advice.

Our favorite Mushkin RAM is at an all time low price. Check my sig for the link to my parts list and the link to the Mushkin.