For troubleshooting, try to follow the steps from here:
http://blogs.msdn.com/remusrusanu/archive/2005/12/20/506221.aspx
Also, see this post:
http://www.sqljunkies.com/WebLog/ktegels/archive/2006/03/08/18625.aspx
If I'd have to guess, I'd say you don't have a database master key:
http://msdn2.microsoft.com/en-us/library/ms174382(SQL.90).aspx

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HTH,
~ Remus Rusanu
SQL Service Broker
http://msdn2.microsoft.com/en-us/library/ms166043(en-US,SQL.90).aspx
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