I finally got sick of having to use Hulu on my MacBook Pro instead of my Ubuntu desktop and decided to see if I could fix the Flash player problems. It turns out that the fix was simple. This article from Ubuntu Geek makes it easy. Since I am running a 64-bit OS, I used the 64-bit instructions:
wget http://queleimporta.com/downloads/flash10_en.sh chmod +x flash10_en.sh sudo bash ./flash10_en.sh
Now Hulu works just fine in Firefox on Ubuntu.