If flash if your problem, you might try following steps that newcolour posted:
For me, everytime I would try to run Hulu, I saw a quick flash of the following error message before the entire screen went blank:
I tried to install the lastest version of flash, and while that helped Firefox, it did not fix Boxee. I looked at newcolour's instructions, but I did not have the files in the same location.
I just did the following and Hulu video now shows properly:
I tried just copying it, but for whatever reason, I kept getting that same Hulu-Adobe error message every time I would restart Boxee.
sudo ln -s /usr/lib/adobe-flashplugin/libflashplayer.so /opt/boxee/system/players/flashplayer/xulrunner-i486-linux/bin/plugins/libflashplayer.so
Hope that helps. And hopefully for me, it will continue to work.