We encountered this problem at the same time as upgrading to VFP 5a so naturally I assumed the upgrade to be the cause.

It seems that in 5a WindowType is readonly at runtime (certainly the manual says that it's readonly once the form has been displayed).

The work around that we have, is to use the show method for optionally modal forms.

IF ThisformShouldBeModal
THISFORM.Show( 1)
ELSE
THISFORM.Show()
ENDIF

Regards
Mark