It's sometimes luck of the draw, I have a q6600 that I could never get past 3.0ghz on my previous mobo. Yet reviews and benchmarks showed people with the same chip and same board got to 3.6ghz very frequently. So I bought a new board, and can OC that same chip to 3.6ghz now. At 3.6ghz my quad core wants 1.375 volts. At my usual settings of 3.2ghz it takes 1.30v.
Did you read the sticky in the Overclocking forum section about how to OC core 2 duos? If you do everything by the book, and it still won't OC, you're chip is a stinker or your board is.
Yes I have a ASUS P5kPL-CM mobo and I can't get past 3.0GHZ
What I am running on my new system is Dual core 2.4 overclocked to 2.89GHz (Second Gaming PC)
I have two systems and this is my newest one I build...
But maybe if I have gotten a 3.0GHZ Processor I don't think I would have that issues because I can change the Volt core on the system.
Raise the memory timings. Also, if your timings include command rate for mem, set it to 2T instead of auto or 1T. What voltage are you running? Also, have you raised the other board voltages? I think its GMCH and the other one...