This question already has an answer here:
I just got a new computer, installed Mist 0.8.8, synced the entire blockchain, then copy-pasted a UTC wallet file from my old computer into my new computer's %appdata%>keystore directory. The wallet appears in Mist when I run it. However, all balances are 0. It should have both Ether and DAO Tokens in it (DAO Tokens have already been added to watchlist). When I lookup the address on Etherscan, it shows the correct balances.
How could this occur? How can it be fixed so I make transfers and call contracts in Mist?