We encountered the same problem. We have an application that has run under VFP5 on WNT machines. We have never had a problem with grid displays.

We are changing over to WINXP Professional. After moving the application we received the grid height evaluates to illegal value error.

We changed display values on the desktop to no avail. We then changed the themes from Windows XP to Windows Classic and this solved the problem.

>It looks like it was my lucky month !!!
>To allow users to choose multiple filters on a table, i put a grid on a form.
>clicking on a command button i minimize it to the headerheight value
>
>.mygrid.height = .mygrid.headerheight + 1
>
>clicking on its header i maximize it
>
>.height = heightval
>
>It works fine, or better it works perfectly on all PC but one.
>On this bloody one it gives me the error that the object miagrid has evaluated an illegal value. This doesn't make sense to me.
>
>Alessio
>
>PS Thank you all once again