Oh you guys ^^. But seriously, 4Kids lost the distibution rights to Pokemon and Pokemon USA has since taken all ownership of the anime. We actually don't know the 'real' reason why they changed the Vas, We have two different stories. The 4Kids Vas say they just weren't approached, and were just replaced by TAJ.
PUSA on the other hand, says they can't use the original Vas because of a contract issue, that doesn't expire for two years. This however is true, but like Maddie has said, (the Va for Meowth) it could've easly been broken, and its her choice whether or not to break contract.
That's pretty much the jist, were suppose to pick a side and continue watching the dub. I believe and always will the 4Kids Vas, but what's done is done. And in the long run its just bussiness. So hope this helps!