This kind of issue happens when the memory is not totally compatible with your system.
Stating from this generation of processors http://processormatch.intel.com/CompDB/SearchResult.aspx?BoardName=DP55SB, the memory is being handle by the chip, so it is required to use the correct memory type (speed). Please let me know which processor are you using?
These are some recommendations for this issue:
- Test the system out of the chassis, minimal configuration please. (Motherboard, processor, power supply, 1 memory stick and video card)
- Remove the CMOS battery and leave the system without it for about an hour. Then put it back on and restart the system.