Are you sure your PSU can handle it? You might not be able to overclock, depending on your PSU. Having listed only Logysis does not help us...
Let's assume you have a PSU that can handle it, under the memory section it will have the word voltage somewhere near the word mhz. What you gotta do is you find the ram voltage and just add 0.1 or 0.2 volts and see if it starts.
franciscogalaz, take your video card out of your machine, then try to hook your monitor to the the onboard video card with the other card out of the machine.