You didnt list volts. Did you put any extra volts into it? Chances are you wont oc higher without a voltage bump. Also put your htt multiplier to 3x.
It could easily be your mobo but.... Hard to say. I have an opty 144 CACJE myself on epox 9npa+ultra mobo. I run mine at an easy 2.6ghz with a small voltage bump from stock.
Also if thats the 144 stock aluminum cooler, id watch your temps. Might want to think about getting the dual core copper heatpipe stock cooler instead. They go for a low $15 total shipped. Or of course one of the aftermarket coolers that cost $30+ like the arctic freezer pro or xp-90.