I am using the official client. Yesterday I made a new wallet, so I closed the Bitcoin client and renamed my wallet.dat to wallet_old.dat. After that I started the client again --> Bitcoin App makes me a new one.
I hope this was the right method because now I have the following problem:
I sent money from my old wallet (i renamed wallet_old back to wallet) to the new one but the sending does not appear in the new wallet!
The sending is listed in blockexplorer and is confirmed about 56 times, right now. But Blockexplorer doesnt know the public key of my new wallet address - maybe this is the problem?
Luckly I did not send much many!
Hope somebody is able to help me!
Thank you!
EDIT: SOLVED.
https://bitcointalksearch.org/topic/m.93551 helped me.
For Mac users:
cd yourapplicationsfolder/Bitcoin.app/Contents/MacOS/
./bitcoin -rescan