When bitcoind is generating Bitcoins, does it change the addresses that are used for receiving the block reward? That is, if I mine two blocks with the same bitcoind wallet.dat, will the same address be credited with both of the rewards?
If you generate a new block with "getwork" then bitcoind will always use a new address each time.
If you generate a new block with "getmemorypool", then you decide. You can do whatever you want because you are creating the block data yourself. "getmemorypool" is new with bitcoind 0.5.
Each block reward will be credited to a different address. No more than one address per block is used in the generation process.