>P.S. This is the fourth modal form popping up in a chain of drill-down forms.

More testing and more info:

I tried various other windows and found Messagebox() does not cause the error (maybe because it's really a Windows API call or something outside VFP rendering responsibility), but other renderings, like WAIT WINDOW or DO FORM SomeForm will cause the same error.

So, it's not necessarily the .Show of that particular form, but rather the rendering of ANY form at this point.

Example:

MESSAGEBOX( loNewObj.Name)   && this works
WAIT WINDOW loNewObj.Name    && this does not
DO FORM testform             && this fails too
loNewObj.Show                && the original failing code