If you had even the slightest problem getting the catches on either end of the memory card to do up, then you might have a socket problem. I put some memory in a mobo once and because the thin pcb had no supports directly under the memory socket, it was actually bending, mobo and socket, together. Which ment that the pins in the middle of the memory stick were not quite touching the contacts in the socket properly. I had to temporarly pack out with cardboard, the gap between the mobo and the case, while putting the RAM in. Taking the mobo right out the case may be nesessary, if you can't pack out the gap. You may think this all sounds a bit silly, but you don't need the mobo to bend much for it to not make proper contact. Good luck, Steph.