Adding a note here...
BUG: Unlocking an encrypted after you have started mining will not work, they keep trying mine and to submit and fail.
SOLUTION: For the users: Restart miners AFTER unlocking the wallet. For the coders: Force the wallet to disconnect after unlocking, to force miners to reconnect with new credentials. They are using the old credentials (keys) to submit to the "now unlocked" wallet.
Going to submit a similar bug report to cgminer also, but that is not the only miner program, and I do not use other miners. He might be able to detect something on his side, or force a "revalidate credentials", after x-minutes of mining. (So it does not keep mining on invalid credentials.)
I only lost a hour of mining before I realized it was not accepting my found blocks... Will be real annoying in the future, when blocks are harder to find.
I still say the first thing it should do after connecting, is try to submit a test-block, just to confirm it is working. (Test block would always validate, with correct credentials, but not result in any actual block. Like a clone-chain, that only has block-1 allowed in it.)
Devs please take note to what this guy is saying , I've noticed he has good ideas and solutions , I 100% agree that the minting process should be seamless , and the user should still be able to lock the client .