I have ran it at 240 FSB before with no issues(for less than an hour).
The memory is Micron ...reported as Xerox (256 MB PC3200 DDR SDRAM)
Xerox (256 MB PC3200 DDR SDRAM)X2...everything else is set to AUTO...
Note: the normal POST screen reports ths ram running at 400 megahurtz...so I figured reducing it to 266 would allow for a stable OC.
The other times I changed the FSB to 240 and it was OK was just changing the FSB and leaving everything else at AUTO...but when I tried that this time I still had issues.
What do you mean by "divider"...nowhere in my BIOS do I see settings for 1:1 or 5:4 (is this what you mean by divider) I thought that leaving the memory at 400 MH(since this is what POST shows at stock) means the FSB bump will not affect the memory...maybe I have alot to learn.
First off, this should be in the Intel CPU section. Even set at "400" (DDR400 or 200 memory frequency) which is the 1:1 ratio, if you raise your FSB to 240 then your RAM is also running at 240 frequency (DDR480). With the Asus mobos, the 5:4 memory ratio (or sometimes called divider) is "320" I think. That's what I would recommend too.
HT enabled makes overclocking a tiny bit harder. I'd enable HT if possible, because you'll take a little bit of a performance hit with it disabled. The real cause of your instability is probably not the HT.
In this case, I think you are borderline unstable which probably means you need a little more voltage. Try increasing the vcore a little, maybe 1.55v at first and see what happens. Asus is notorious for drooping under load which causes undervolting. You might even need 1.575v. Raising voltages might increase temps a little too. Check voltages and temps for idle and load.