Alert! failed at checkpoint [C3]...... on boot

Hello and thank you for reading this message.

Would anyone be able to advice on error after an upgrade? System is Inspiron 545.

Error is : "Alert! Previous attempts at booting this system have failed at checkpoint [C3]"

The upgrade is PCU to Intel Core 2 Quad Q8400 2.66GHz/4M/1333 LGA775 CPU (SLGT6) which is working fine.

Then the RAM upgrade to 4x 2GB Samsung M378T5663EH3-CF7 PC2-6400 4GB DDR2-800 240 PIN DIMM RAM. 

The original RAM is working fine, which is 4x 1 GB. Both pairs of the new RAM work fine in slots 1 and 3. Then everything is okay with another RAM in slot 3 (so only slot 4 empty). But when part 2 of the second pair of new RAM is put into slot 4 the computer shows nothing on the monitor, and then when rebooting next time with slot 4 removed or the original RAM back in (anything other than all 4 of the new 2 GBs in place), the error message appears on booting, then booting again the computer starts fine.

BIOS are the latest version according to the Dell Driver tool. 

Thank you.