Abit IC7 Help?!

Hi guys, my first post here but I hope some one can help me as this is driving me nuts!

I have this rig:

Abit IC7
P4 2.4C - SLK900 -
2x512MB TwinMos 3200 ( dual channel )
GeForce 4 TI4600

Now, im running the 2.4 at 250FSB and ram at 200. Works great. and the CPU is running at about 56c MAX - i mean hot day full load.

So i figure i have room for abit more...

I tried running it at 275 FSB, 3:2 so ram was at 183 ( lower than before ) wacked up the CPU voltage abit, and it wouldnt boot, so i reset CMOS, tried 260 FSB on CPU and 3:2 - with again fairly high voltage - it wouldnt boot.

So i reset the CMOS - put it on 255- still wouldnt boot...... Back to 250 it went ok, the Bios says MAX fsb of 412 ? and i know loads of other people have taken this board to 300-350 without problems.

I re-seated the northbridge with some proper thermal compound, after about an hours worth of getting that bloody pad off, and after it had bedde in it booted at 260FSB - but after i started using it IE died, desktop looked VERY erm, dodgy... Images were strenched all over the place then it had an error, something about changing RAM to HDD ? or something... - back to 250 and my CPU is begging for more, any one else had this problem ? any one got ideas on how to fix it?

Just so you know, the northbridge doesnt feel very warm... so I'm not 100% sure if it is that.

Thanks for any replies