NativeWindowBoundsEvent is part of the AIR runtime. Your error log show you are trying to run this in Flash Player.
Flash Player doesn't know what this class is. Make sense?
Many thanks Mike ..
What ever you said could be a valid point . but do u have any suggestion / solution to overcome this problem ?
We had a similar problem in my project. Took a lot of research and trial and error, but we finally narrowed it down to the resource.properties file. Turns out that if the file gets too big it causes this problem. Extending the timeout doesn't help. You have to break your resource.properties into more granular files to reduce the file size. This seems to fix the problem. We have had it happen several times since then and we know how to fix it, so we get it fixed pretty quickly.
Not sure if this will fix your problem, but it fixed ours.