I don't know if this will fix your problem, but you should take out the 'scope="request"' attribute from your action. The scope attribute refers to the scope that an ActionForm should be placed into. Your action does not use a form as you defined it, so the scope attribute is probably causing a problem.
The scope attribute doesn't fix it. I have no idea where the problem comes from. Is it possible, that the parser throws just an exception but doesn't know where the real problem is. Maybe it is just a randomise parser exception?