I assume you realise for dual channel with 1 pair you need to use slots 1 and 3, not 1 and 2? some boards don't like using 1,2,3 for instance with 3 sticks unless you either disable dual channel mode entirely first in the BIOS or swap to flex mode if the board supports it (not reccomended). For normal operation with 2 sticks of RAM do not use slots 1 and 2, if your using 4 sticks and slot 2 still isn't working then its RMA time.