You could possibly be running into problems with all four dimm slots filled with memory. In fact Corsair usually recommends downclocking your memory when filling all four dimm slots. See here:
Full dimm slots - Please school me. - The Corsair Support Forums. Follow the links posted by DereKT.
Also be aware that the more memory your v-card(s) have, the less system memory you have for non video system resources under a 32bit system since 32bit OS' are limited to 4gig of memory. See here:
http://www.corsair.com/_appnotes/AN8...e_Analysis.pdf.
Other then that, make sure you have "manually" set the recommended memory timings and voltage as stated by the RAM manufacturer.
Good luck