I have the same motherboard and did a little reading. The chipset on these motherboards was not really designed for the 800MHz, but it was still used by ASUS anyways. I have reduced the FSB speed on my system for increased stability. Here is the posting from another site which I found.
The 845PE Northbridge was designed for FSB400/FSB533 processors,using DDR266/DDR333 memory. (See page 11 in the Intel spec.)
No matter how many different models of this motherboard that
Asus made, it is still based on the 845PE. Operation at FSB800
with DDR400 memory constitutes overclocking, and overclocking
comes with no guarantees (only Intel can test the chips and
bin them for speed, and the chips are not tested at FSB800/DDR400, so Asus has no way of knowing how far they can be pushed).
I've read descriptions of other people's luck with the 845PE
and it is described as "I can set the clock to 200MHz and
not a stitch more". That means even in the best case, there is
absolutely no margin left. The fact that your board runs stable
at 190MHz, instead of 200MHz, should not be a surprise, as Intel only has to guarantee the chips work at 133MHz (for FSB533).
The sin being committed here, is the user manual should state
that "overclocking comes with no guarantees". Persons interested in buying FSB800 processors, should be buying a P4P800/P4C800 or equivalent board, as the Northbridge chips on boards like that are guaranteed by Intel to run at FSB800.
If you want rock solid operation, pair a 3.06/FSB533/512K
Northwood processor with the 845PE Northbridge.