asus a7v600: problem putting in new memory

hi all...

first time poster here, hoping someone can help me with the following problem:

the above mother board has three memory slots that support ddr 2100/2700/3200 dimms.

i have 2 512mb ddr2100-256 dimms in it currently, but want to upgrade to 2 gb of 3200-400m (2 1gig sticks).

now the only way i can get the old memory recognized is by having the dimms in slots 1 and 3; if it isn't configured that way, i get the post code for no or bad memory.

so i pulled out the old memory, then inserted the new stuff in the same configuration, and was rewarded with the no or bad memory post code.

so i tried every configuration i could think of (both dimms in slots 1 and 3; slots 2-3, slots 1-2), then individually in each slot. the only configuration that works is one dimm in slot 3, for a total of 1 gig of ddr ram.

my motherboard manual indicates the board supports up to 3 gb of ram, but there are some limitations on the ddr3200-400 type.

the tables in the manual don't include dimms of 1 gb in size (only up to 512), but no the table indicating ddr400 ONE dimm support ONLY, samsung ram (which is what my 1gb dimms are) is listed. on the table for TWO dimm support ONLY, there are four brands of ddr400 ram listed, none of which is samsung.

so here's my question: will this motherboard only support two gb of ddr400 ram (despite the manual stating you can put 3gb in it), and then only if it's a certain brand?

thanks for any help you can offer!

steve

thx, mondoman.

the dimms, btw, are double-sided (8 a side)

now another question:

how much performance am i losing by clocking down to 333?

thx again!

steve