It is possible. Some versions of the player slow down the frame rate when minimized not visible, so that could be a factor.
I've seen Flex UI's be shrunk so small that negative numbers get passed into the player and an exception is thrown.
I've also seen Flex Uis be shrunk to the point where some component can't decide if it needs scrollbars or not and then the components never get to creationComplete.
Can you give me an advice what could I do and can I do anything at all?
I would try running in the debugger and see what is actually going wrong.
The key API for creationComplete is in mx.managers.LayoutManager's doPhasedInstantiation. It should get called several times during startup but then should stop being called after all the creationComplete's are dispatched.