I have the strangest problem!

I've got a Canvas with a Thread as engine that shows the user that the program is busy (with downloading stuff)!

If this Canvas set as current displayable after a Form was displayed... a empty Canvas appears. And dispite the many repaints the engine calls I won't appear

Now the strange thing is that sometimes when the Canvas is set as current after another Canvas was showed the Canvas will be painted in the good way ???

Does anybody has a clue?