I must note that I’ve wasted considerable amount of time on this error message. When copy/pasting, I’ve failed to close a bracket in a HQL query, and even more – the bad expression exceeded the screen space and without an editor that would complain, once again (remember NHibernate “Could not find the dialect in the configuration” “Could not compile the mapping document”) – I was left alone with NHibernate error handling :(. And it did not only complain about query aliases – it complained even about the mostly used mapping names.
The good thing is that I revised my NHibernate mapping knowledge and querying capabilities which turned out to be a great confidence booster. However, I still can’t tell if this is only a problem with an oldish 2.0 NHibernate version or not.