It's when you open a query? I would think that would be related to a combo box. Did you just change a combo box on a form and are trying to leave the form now and go to a query?

This is the message I get when I open a query. No forms are opened

It looks to me like you are limiting the records in the query based on the the value from somewhere and the query can't find it.  Is the query meant to be run from inside a form?

Can you post a screenshot of the query in design mode please?

The query is run by itself. There is no form associated with it. The Starkey table however gets its information from an excel table outside the database

Does it work without the criteria? You may have to aggregate in one query then feed the results into a second query and then add the criteria.

In addition to the question by Kevin :

Was this working previously and now it is not?  Or, Has it not ever worked?

Is the Excel table a linked table or something you import?  

If there are any "strange" characters in the Excel it might be causing issues.  
If it was working before, has the information changed in any way for that Excel so that it could be that it is not matching up to your query fields properly?