PermissionsGrayedOut\CannotRunProgram

We installed an upgrade to our XP, from a CD Rom. After installing the

upgrade, when we try to run out software app, we get an "access denied

user does not have permission to run this program. Please contact the

network administrator." error message. If we select a file in the

program folder, right click it and choose the security, some of the

users have the read\readwrite boxes checked, but they are grayed out.

We cannot check or uncheck any of the boxes. What would cause this?

TIA