It happens with old style forms (@Say/@Get). You've to disable Themes to fix the problem. It can be done on the form or application level using Themes property.
>
>It doesn't ocurr all the time but ocurrs. I'm testing a form (I execute program as I was working with it) and suddenly all controls disappears... If I move the mouse appears one by one but I move again and disappear again... There's no instruction hide I performe in any class. No client told me about this so I think only happens when I'm developing and testing but I'd like to know if anyone of you has had the same problem.
>
>