Thanks Ariana and Dimitry, Actually, it turns out to have been more simple than that... I think I had put a "?" into the name of a parameter I had created, intending to only put the question mark into the display prompt field. I guess having a question mark in the name of the parameter is something that confuses CR. Once I replaced that, all seemed right with the world again. Thanks again! David From: The Museum System (TMS) Users [mailto:[log in to unmask]] On Behalf Of French, Ariana Sent: Friday, October 16, 2009 10:46 AM To: [log in to unmask] Subject: Re: Invalid Procedure Call or Argument ...just thought of another thing to check: did you make a change to a formula? A formula dealing with either manipulating a string, or changing the data type of a field to something else, and trying to evaluate it? If so you may want to try commenting out the code and try it again. I hope some of this helps, I know how frustrating these errors are. Ariana From: The Museum System (TMS) Users [mailto:[log in to unmask]] On Behalf Of Aylsworth, David Sent: Friday, October 16, 2009 11:25 AM To: [log in to unmask] Subject: Invalid Procedure Call or Argument I need help from you crystal reporting experts!! I made a slight modification to a crystal report that had been working fine, but when I tried to run it, I got an error message that I don't recall seeing before: "Invalid Procedure Call or Argument". When I reverse what I did, I still get the same error message. Do any of you have any idea about what it is referring to and how do I fix it? Thanks, David David Aylsworth Collections Registrar Museum of Fine Arts, Houston telephone: 713-639-7824 fax: 713-639-7780 Opening Sunday: The Moon: "Houston, Tranquility Base Here. The Eagle Has Landed"