microphone problems w/ no opportunity to re-test
It seems that you may need to provide a way to re-test the microphone setup. In the initial pass where the microphone was introduced, your application could not hear anything. Obviously something wrong on my end, but you did not offer an opportunity to re-test this once I thought I had resolved the problem.
The problem is "How do you get back to that screen?" I still have some mic issues that appear will need a bit of 'Trial and Error" to work out. FWIW, I've never seen the mic and video working with flash on this machine before. (never tried it, don't know of a way to test this independent of duolingo.)
Go here: http://www.macromedia.com/support/documentation/en/flashplayer/help/settings_manager06.html and always allow duolingo.com. This worked for me, solution was posted here: http://duolingo.com/#!/comment/1618