DRAM Slots

My JETWAY 810 board (the one with lousy onboard AGP and no AGP slot) has two DRAM slots. Flirting recently with overclocking, I got my cellie to run from 366 to 412 MHZ. I have used it for weeks and has proven itself quite stable. Checking out my new Micron 128MB PC133 module, I found that I couldn’t overclock my rig when I have memory attached to my second slot. I have tested the MICRON w/o my old but amazing APACER on the first slot and the system runs fine at 412MHZ. The rig always crashes when overclocked using any of the modules alone on the second DRAM slot. Is it possible for the two DRAM slots to have different stability levels? Why does my 32MB PC100 Apacer score better at SANDRA than the 128MB PC133 Micron?