>>We are using SQL Server Standard 2008. Several of the columns are encrypted using a symmetric key. The key is opened when the application is launched and kept open until the application is exited and works as expected. While using the app the key is somehow being closed. Requeries are returning nulls instead of decrypting the data. Any ideas as to how this is happening?
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>The key will be closed when connection is closed. Make sure that you're not closing and re-opening connection in your application or open the key when you are re-opening connection. You can check for open keys using sys.openkeys system view.

Thanks for your comments on this. We found the problem buried in a trigger. It's always the last place you look.