First, check whether your transaction executed successfully using a blockchain explorer like https://etherscan.io/ or https://etherchain.org/.
If your account balance includes the transfer, then it is most likely a problem with the syncing of your blockchain data, as
If it is a syncing problem, and your computer runs on a hard disk drive (HDD) and not a solid state drive (SSD), the reason for your syncing problem is due to the recent attacks on the Ethereum network. The attacker sent many many low cost transactions that caused the blockchain node clients to slow down, and the hardest hit are clients running on HDD drives.
The solution if you have a HDD drive is to either upgrade your computer to a SSD drive, or wait until the next hard fork when the node clients will attempt to remove some of the data that slows down syncing. The latest update on the upcoming hard fork can be found at [UPDATE] Hard Fork Block Number Delay [10/31/2016].
If you have a SSD and more than 4 Gb RAM on your computer, clear out your old blockchain data by deleting the
chaindata directory on your computer, or finding the
geth executable and executing
geth removedb to remove the old chain data. Then run Mist and it will attempt to sync again.
chaindata directory can be found in:
(Remember not to delete your
keystore directory as this directory contains your private keys).
All of this assumes that you have the latest 0.8.7 Mist (or Ethereum Wallet).