When using our standard forms you may occasionally see "Warning: This page already exists, but it does not use this form." It's often probably wrong.
We may try to reduce the frequency so that you get that message only when it's true.
Even if it is true, you need not generally be concerned. The commonest situation is when you are upgrading a page that's not yet in the SMW system. You should be getting praise rather than a warning!
-- Robin Patterson (Talk) 02:15, January 5, 2013 (UTC)