I've never encountered this error before myself. You'd think that there would be a simple solution: make sure you don't have a RETURN statement anywhere in your VBA. But if you HAVE no VBA in your form, what's the deal? Well a quick Google search gave some ideas...

One user suggested that this could occur when you have an error in a Form_Load (or Open) event in a subform, but there is and empty Load event in the parent form. So if you have a subform, check for that.

Luke Chung over at FMS (another Access MVP) suggests that this may occur when your VBA has become corrupted. A Compact and Repair only works on the tables. Decompiling your database can fix corruption and avoid strange errors like this.

Also make sure you are not missing any References. VBA editor - Tools - References. Make sure nothing says MISSING.

Thanks for the help. I found that if I have the list form open the detail form with a button rather than a double click event, I do not get the error. I have seen this error before but never when VBA was not present. I am using Citrix and the servers are in Belgium. The system is not up to date and I sometimes I get strange errors with other applications as well that are only fixed when I log out and back into the system. I appreciate everyone's input.

I've gotten weird errors too using remote Access databases while logged in using PCAnywhere or Windows Remote Desktop. Something about it just causes strange behavior.