Hi Sades, I think its FB 2 that is the problem, ive tryed FB2 and FB2 Beta (the Beta is for HTML Editor 3) get errros with both of them, atm i dont use FB2 in that way AS2 works as it should.
Yes i have tryed edit forms with FB2 too, that is not working and as you say it creates loads of Java errors.
Uninstall FB2 and AS2, delete cache, then reinstall AS2 that should make AS2 work.
Regarding your Header already sent, check that you dont have dublicated Start session on your pages.
hope this helps you out a bit.