In your bios (and in some tweak software), you will see something like:
Memory timings/DRAM configuration:
Divider/Speed/Etc: 133 (166, 200, etc)
Cas: 2 (2.5, 3, etc)
Trcd 2 (3, 4, 5, etc)
TRP 2 (3, 4, 5, etc)
TRAS 5 (6, 7, 8, 9, 10, 11, 12, etc)
Some other setting: 1T (2T)
The fastest possible settings (and most unstable settings) are lower and on the left. Normally people just write them out as 2-2-2-5-1T or 2.5-4-4-10-1T. Just take a look at what they're set at now and start increasing them to see if it helps.
Also, as with my venice, ram is usually less stable when run on a memory divider. For example my ram runs at 280mhz when at 1:1 (no divider), but only around 220mhz when on a 166 or 133 divider (may have something to do with my particular processor's memory controller).
Your ram sounds like it's pretty good (don't know the exact specifications), but you may actually be able to run it on a 166 divider at 240mhz. Just set the timings as low as they can go ( 3-5-5-10-2T) and work your way up from there. I'm only saying this because some people have better luck with some dividers than others.
To check the maximum speed your ram can handle, set the multiplier to 200 (1:1), set the cpu multiplier to 5, set the htt to 3x, set the vdimm to 2.8v, then start increasing the HTT until it will no longer boot or pass memtest.