|The cpu fan must be plugged into the cpu fan header, otherwise most recent or fairly recent mboards will shut down in a few seconds.|
You must have both the wiring for the female connector for the main 24 "pin" power socket on the mboard, and another female connector for a smaller socket on the mboard, connected from the power supply.
The Radeon 5750 card has a small socket a connector from the power supply must be connected to.
Ram that requires more voltage cannot damage the mboard, the bios / mboard can make other voltages available other than the standard voltage, but the higher voltage ram may not work with the mboard.
Corsair does not list ram for your GA-P55-UD3 , but it lists 1600 ram for the GA-P55-UD3L .
If the part number for the modules you got is on the list, Corsair lists them as working with your model.
If the part number for the modules you got is NOT on the list, then there's no way of knowing whether they will work.
Other sites I looked at do NOT list 1600 ram, but the ram they list for GA-P55-UD3 and GA-P55-UD3L appears to be the same.
"Without any RAM installed, the LEDS flash and the fans spin for a second then shut down then flash and spin again, and repeat."
That's not normal at all for when no ram is installed. Something else is wrong. Do it do the same thing when ram is installed?
It is easy to test for incompatible ram that has caused your mboard to fail to boot.
Make sure you have a speaker or speakers or the equivalent connected to the mboard so you can hear mboard beeps (see your mboard manual if you need to).
Remove the AC power to the case/power supply.
Remove all the ram.
Restore AC power.
Try to boot.
If nothing else is wrong, you will get no video but you will hear a pattern of beeps that indicate no ram is installed, or a ram problem.
E.g. for an Award bios or a bios based on one, that's often a beep of about a half second, silence for a half second, a beep of about a half second, silence for a half second, continuously.