In rare cases the wallet cache needs to be rebuilt. For example when the wallet cache isn't compatible with the current wallet version. How do i delete the wallet cache and trigger a rebuild?
In your wallet folder* you have three wallet files.
<walletname>.keys <walletname>.address.txt <walletname>
The wallet cache is the file without an extension. If you delete or move that file to another folder the cache will be rebuilt when opening the wallet.
Note. It is advised to properly backup your wallet files before you perform this action. Also note that deleting the wallet cache results in losing some of the transaction history, namely recipient addresses and private tx keys. Thus, if you want to use an existing wallet with the GUI, it is advisable to backup your wallet cache in case you need transaction history info in the future.
*The wallet folders are as follows:
Mac OS X: