>I can recreate the table, in that there are not problems, what I worry about is to know the problem, to avoid that happen the same in other more important table, I also proved making a query toward another table and if I want to modify this new table, it happen exactly the same thing. Atributes are fine, i checked them,another thing, Use not fails , it fail after i make the changes and i want to save them.

You can't modify a table that was opened implicitly by doing a qeury against it - it has to be used exactly one time EXCLUSIVE, or the modify structure command shuts down and refuse to make changes - it also warns you by telling you that the table is open for mods Read Only in the title bar - not mdofications will take, and in fact trying to make a modification shuts down the structure modification dialog box, returning me safely to the command window.