What are the EXACT models numbers of your CPU, motherboard and memory kit?
The rest of your hardware specifications including EXACT power supply model, are also helpful.
Up front we need to know, have you taken the CPU back out and made sure there are no bent pins on the CPU or motherboard, depending on whether you have an AMD or Intel platform? Yes, bent pins OFTEN results in memory errors and problems, so ruling that out first should be the primary consideration.
Also, some backstory for this build regarding whether they are new or used parts and what you have actually done so far, would also be helpful.