[CS3] Just started and already stuck

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?

You did not convert the rectangle to a symbol, you just created a new (blank) symbol. Delete everything off of your layer, and start again. Drag out the rectangle. Double click the rectangle and then press F8. Fill out the information and press OK. NOW it is a symbol. Now you can do any tweens you want on it. You may want to delete the old empty symbol from your library.

Cheers,
Mavrisa

Thanks. Now I understand want went wrong. I've used Ctrl+F8 instead of F8.
Grrrrr.