Flash Builder 4

Hello, is anybody using Flash Builder 4 to develop Flash extensions?
I have used the demo of Flex Builder 3 before, and now bought CS5 Web Premium which comes with Flash Builder 4, and it doesn't seem to be compatible. There are lots of errors that occur and prevent me from building, for example:

m_dwStartAngle = (int) Math.max(param * (Math.PI / 180.0), 0);

Description	Resource	Path	Location	Type
1086: Syntax error: expecting semicolon before Math.	CRunMvtclickteam_sinewave.as	/RuntimeFlash/src/Movements

Francois - Did you use Flex Builder 3 earlier and upgraded to Version 4 later and simply imported your old project? I started a new project from scratch, that might be the problem.

Thanks Jamie. After fiddling around a bit I found such an option and fixed that particular error.
Go to the properties of the project, select "Flex Compiler" and select "Use a specific SDK: Flex 3.5".
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EDIT: Solved the other errors as well, ouch...
If you get something like "unable to resolve '0000.mp3", you did in fact forget to build an SWF application while holding the shift key in MMF.

Thanks for your help!