Welcome to the forum.
Getting an EP45T or EP45C motherboard to run DDR3 memory at its rated speed can be a real challenge.
Many had to start with lower memory speeds such as 1200 - 1333MHz and work their way higher with a lot of stress testing.
If your G.Skill memory is rated at 4-4-4-12 at 800 MHz, it might be able to run at 1066 - 1100MHz with 5-5-5-15 timings.
If your Patriot PC3-12800 memory is not designed to work with P45 systems, it will probably take a lot of effort be stable.
There might be a problem with the first x16 pci-e slot.
You can try using the second x16 pci-e slot to see if this makes a difference.
Which version of the Geforce drives are you using?
Which motherboard bios are you using?
I suggest getting your system completely stable with stock cpu speeds.
With your P45 system, I doubt that using DDR3 memory at higher speeds will make a noticeable difference.
Mr preference is to run DDR2 memory with cas4 timings at 850 - 875+ MHz instead of using cas5 at 1066MHz speeds.
Please post links to the full specifications for each of your memory kits.
Including a screen-shot for the pre-programed SPD specs will help.
Check out EP43-UD3L with Q9400 wont post, keeps rebooting, post #5 for recommended basic settings at stock speeds.
GA-EP45-UD3P - Won't boot with 450FSB is an excellent P45 overclocking thread, where Dan did an excellent job posting his bios settings and useful screen-shots. The EasyTune6 information is very useful, but I would never use my system with ET6 running or in the system tray. You are hereby warned, it is a very long thread.
It is critical that MCH Core voltage is set correctly, too high or too low will cause boot loops or instability. You will probably want to set DRAM Voltage at or near its maximum rated voltage. There are additional voltage tweaks that will need to be used when overclocking your cpu speed. The best overall performance will be in the 3.80 - 4.0 GHz range using the highest Cpu Host Frequency setting that is stable. Your EP45C-DS3 should easily use 450 - 475MHz and possibly higher.
Let us know which stress testing programs you are running and provide detailed information about any errors or problems.