I think Nesov is right, you've basically (re)discovered that the universal prior is uncomputable and thought that this result is related to Pascal's Mugging because you made the discovery while thinking about Pascal's Mugging. Pascal's Mugging seems to be more about the utility function having to be bounded in some way.

You might be interested in this thread, where I talked about how a computable decision process might be able to use an uncomputable prior:

http://groups.google.com/group/one-logic/browse_frm/thread/b499a90ef9e5fd84/2193ca2c204a55d8?#2193ca2c204a55d8