its probably not RAM or ROM. You would most likely get the dreaded "sound board interface error" upon power up if it were one of those.
More than likely you have something wrong in the "mixing" or muxing circuit. Or, one of your 8910's could be bad and the good one is only responsible for the two sounds you are hearing. If you have another known good 8910 that would be the place to start.
Otherwise, could be any number of problems.