problem with an old wallet.dat file

[k99]

hallo,
i have a problem with an old wallet.dat file. i bought some coins in april 2013 and now wanted to run the actual mac qt client to see my balance there. i copied over the backuped wallet file to the standard directory (where the new generated wallet.dat was). but when i restart the client the balance is 0 (network data all synced). are there some known issues with changes in that timespan?
i heard of some data corruption problems with the qt client on the mac. i hope that has not destroy my wallet!
hope some one can give me a hint! thanks in advance!

EDIT:
I just have found a backup of the whole folder and there are luckily my coins. seems if you set up a new client with encryption the old wallet file is not supported anymore.

[Martijnvdc]

Try looking up the addresses on blockchain.info.
blockchain.info/address/<address here>

See if they have a balance.

[escrow.ms]

Do a rescan.
Start it from the command line with the -rescan option.

[k99]

thanks for your answers. already found a solution (see orig. post).

[Martijnvdc]

Great