I started out with two modules and later bought two more. The manufacturer swapped the label positions on me, so I accidentally put them in backwards, assuming they were identical to the first. Long story short I turned the motherboard on and smelled some smoke.
There was a 10cm long by 4mm wide rectangular hole in the motherboard a few inches away from the four memory slots. I made the mistake of using too few standoffs because I was running short, and I'm wondering if the motherboard short circuited by touching the back of the case, or the backwards memory somehow caused this incision several inches away from the memory slots, or if something else might have happened that I'm not aware of.
Anyway, that motherboard is toast and I'm building a new one, with enough standoffs and light this time. I'm wondering if there's any danger in trying out my memory in the new board. They don't look visibly damaged. I've included a link to my dropbox with pictures of them, and I'm wondering if anyone could comment on the safety of trying to use these modules again.
See the slot in the memory connector in the picture? The motherboard slot is keyed so you cant insert them backwards but I guess everything is possible with brute force and ignorance. You will be taking a chance using them again after they caused the board to short and burn.
If you turned on the PC with the DIMMs brute-forced backwards then the motherboard and DIMMs likely shorted themselves out.
As long as you have standoffs near all four corners and preferably at least one near the center of the board, it is very unlikely that the board would short to the MB tray unless you press really hard on it while the computer is running... but then, that would not be recommended even with all possible standoffs installed.