strange problem for wallet

[supercanada1]

I created a coin and mined a lot of coins for testing, I send the coins to another wallet b, it works, after some confirmations, the coins in the wallet b still cannot send out although it says spendable, even after some confirmations, it shows transaction fail if I try to send some out, so I copy wallet.dat to a different computer it works, why?

[CoinThug]

I created a coin and mined a lot of coins for testing, I send the coins to another wallet b, it works, after some confirmations, the coins in the wallet b still cannot send out although it says spendable, even after some confirmations, it shows transaction fail if I try to send some out, so I copy wallet.dat to a different computer it works, why?

Wallet won`t unlock. What do in need to do?