That speed seems suprisingly low for a 2500+ Barton.
Most seem to be able to hit 2.2ghz or higher without problems, and with little added voltage (most do not need more than 1.85V or so), even with the stepping you have.
I bought Retail from Newegg and I recieved the stepping listed in my signature. Steppings however, do not seem to make much difference in the Bartons. Seems you just had bad luck in the overclocking lottery (don't worry- it happens to us all one time or another).
What board are you running? If it's not a decent Nforce2 board, I would seriously consider upgrading to one, as KT400's and older boards do not overclock nearly as well, even though the problem may seem to be the CPU.
If all else fails, stick that sucker up on Ebay, or just plain sell it, and try your luck again. Remember with overclocking, picking a chip is mostly luck, you need not return a chip (RMA) because it won't overclock like you want it to.
Many people are practicing this, and believe it or not, it drives cost up for all of us.
Good luck!