To get any system to "wake from sleep" it has to be 100% stable if not this is exactly the type of issue that arises. I would suggest making sure all your drivers and firmware are up to date and then test everything one by one. Try Memtest86+ first by following these instructions exactly. It can take a long time but it it worth doing properly.
Please follow these instructions
exactly.
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.