Motherboard temperature issue. Help?

Ok o I replaced my crappy MSI K9N6SGM-V2 board for a decent gigabyte ga-ma785g-ud3h board so that I could upgrade to Phenom II X4 during boxing day sales.

So the issue is, since I am getting rid of my CPU (X2 5000+ BE), I decided I'd see how good I could OC it. I didn't really need much before so I OC'd to 2.8 GHZ for a little gain as I didn't buy a great CPU cooler.

Now I decided I would try for 3.2GHZ or so and see if this cooler can do it but my problem is my Motherboard Temp.

I get MB temps of 33C on idle, and I was gonna see how far I could push the OC in AMD overdrive then reset and go into BIOS to do the fine tuning. (Wanted AOD for quick OC testing first)
But as soon as I run stress test for AOD my MB temp instantly goes from 33C to 44-45C and rises till it peaks at 54-55C which is kind of high. The 45C jump starts as soon as I hit "Start" on AOD and it rises to 55C in under a minute and stays there.

Why are my temps so high? For fans I have 1 90mm rear, 2 fans in my PSU and a CoolerMaster Vortex 752 CPU cooler. Theres air intakes in the bottom and front of my case but no exhaust at the top. Its an M-ATX case.

I didn't think Air flow could cause the problem as I though the temps would have to gradually rise, or is my motherboard perhaps faulty?