I created a simple flash animation. Everything was ok. Then I tried to create the same animation from scratch and I got stuck .

I opened the flash program, created a new flash file and saved it.
Now I click on the rectangle shape tool and drag a rectangle on the stage.
So far so good.
Now the selected rectangle becomes a new symbol (type: filmclip).

Now the stage turns into a very large white area with a little + in the middle,
and the item in the library is not the rectangle but the same +.

Later on, when I want to move the rectangle using the timeline I get an error when I turn the tweening into "motion".

The message: "Motion-tweening is not possible on layers with ungrouped forms or on layers with more than one group of symbols."

What to do?