Help! New memory didn't work, Now old memory won't either

Ok, I've had my rig, second one in my sig below (the 1700+) up to 2.5 with no problems. But I wanted to upgrade my old Corsair XMS PC2700 512 chip to two sticks of Mushkin Level II PC3500, so as to use the duel channel memory function of my NF7-S mobo. So when I replaced the Corsair with the Mushkin I didn't change my BIOS settings, I left them set for the 2.5 oc. After changing the RAM, I fired up the computer and it locked. So I cleared the CMOS and started it with the default settings. It ran fine. Then I started trying to oc it. I never could get it to oc very well, so I thought I'd just put my old RAM (the Corsair) back in. Well now it won't do much better than the default settings. The best I could get it to, after LOTS of reboots (trying different settings) is 2.210. Arrrrrugh!!!!!!!! I don't know what I screwed up, but I haven't figured it out yet. I've kept a written log of all the different settings I tried. I even tried just setting itback just the way it was before I messed with changeing RAM. But I'm still stuck! It's probably something simple that I just overlooked (I hope!!!). Anyone have any sugestions?

bump

that same thing happens to me all the time. i just got this new PS (replaced a NO-Name 400w) first OC i went to 220x11 and prime ran for 30 min. then i went to 225 and it locked. reset cmos and it wont hit 220xanything anymore. Heck, it wont hit 210x anything.
i feel your pain.
good luck