What multiplier and FSB are you using for those ratings? You say 133MHz, but does that mean that your RAM is only certified for 133MHz or that you're actually running it at that? I doubt that, since 901 into 133 is something like 6.7...and I don't think that the motherboard has a 6.77 multiplier... :-)
It's quite probably your IDE devices suffering here. You're probably tossing the PCI bus up further than it can go. Make sure your PCI bus isn't tied into the memory timing in the BIOS so that it's locked to 33MHz. Good thing the Abit can do this.

If you do this, then you shouldn't have to worry about which video card you have, as they'll be more or less unaffected by the changes to the FSB/multiplier. By the way, I'm sure you know, but multiplier overclocks are generally safer, since they keep memory timing in sync. If you are having trouble hitting a multiplier, though, see if you can find a PCI bus between 30 and 33, and then factor it up to whatever FSB you're using (For instance, if you pick 31, and you were running at 133, you'd now be running at 125). Once you do this, your PCI bus will be underclocked (Which is safe, but not the greatest thing in the world), but you'll be able to crank up the speed and hit higher without the peripheral dependency.

In other words, if cranking up the FSB doesn't work, throttle it back and jump a multiplier. Then try again.

Also, as I said, you can get more stable overclocks if you don't use 2-2-2 latency. The lower latency means that the memory is more sensitive to timing errors in the system. If your system is cranked up and busy doing stuff, you may need that extra margin for error.

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"And knowing is half the battle!"