The default running frequency for a 2400 is 1.8ghz,
Wow good god an entire page of incorrect information.
The 2400+ XP chip's DEFAULT speed is 2GHz people. Don't try and argue this because I have both the 2400+ XP and the 35w 2400+ XP-M <---- THAT one is default 1.8GHz speed.
With stock fan and no case fans and my side panel open my 2400+ ran at 64C IDLE, I put on the heatsink from the coolermaster jet with some AS5, took a 60mm and 80mm fan that spun opposite directions but blew air in the same direction to get a compressor and my temp is at 54C Idle....but that's beyond the point. I don't know why everyone is telling you that the default speed is 1.8GHz because IT IS NOT I'll take a damn screenshot of my 2400+ running at it's default 15x133 and I assure you that doesn't equal up to 1.8GHz, it's only the mobile version that's 1.8GHz by default.
Are you sure your heatsink is properly seated? Do you have an aftermarket heatsink? Did you apply new grease to it, but failed to see the existing thermal pad on the stock heatsink because that will cause all sorts of problems. I've found that the 2400+ XP's like to run kind of hot, you, me, and numerous people in forums I've seen have high temps without adequate aftermarket heatsinkage or good case cooling.