I've only seen this issue when there is a version mismatch between Flex and the Flash Player.
This is actually the 2nd time I've seen this question in the past week; the other person said that by changing the SDK from 3.0 to 3.5 the problem went away. I wonder if Adobe changed something with the download recently.
Thank you Mr. Yeffrey!
I have all ready Updated the SDK to 3.5 and it did it... ( )
(Just came back to clear my post... but, saw your answer).
Thanks again for the quick reply!
Here (In Budapest, Hungary) is New Years Eve... So Happy New Year!!!
Herendi Kristóf Pál
Glad to hear you solved the issue. It's New Years Eve too; the year turns in about 6 hours.