Thank you very much Fabio,

This is very strange, i also reinstalled the vfp. I did what you said, and still the same problem. I added this code, at the end of all the lines in the "activate" property of the form:

* Break when an expression becomes true
IF VARTYPE(principal)#"O"
WAIT "Reference lost" window
ELSE
WAIT "Reference Ok" Window
WAIT VARTYPE(principal) Window
ENDIF

And shows: "Reference Ok"


And i added a button on the form with the same code on its "click" property, and when i click this button, shows: "Reference Lost" :(

Why? I don't know :( But the reference is lost.