Well you could try setting the timings and voltage manually for the 1600Mhz speed. However I suspect that there is a problem with one of your sticks as they are good modules and normally run very well with no problems. I have four of them myself in my review machine.
I think the next thing is to test the modules one at a time. It does take time but follow these instructions
exactly please.
I would suggest that you download and run the latest version of Memtest86+ to check your RAM first.
Memtest86+
http://www.memtest.org/Insert
one stick of memory in
slot 1 and run Memtest on it for at least
10 complete loops/cycles and if there are no errors then swap it over with the next one and continue untill you have checked all modules.
If you have any errors the module is faulty.
If you have any faulty modules you will have to return the whole kit as they are matched.
Post back when you have done that with the results.