I know a LOT of people still have a frozune after many many battery drains and resets and all that stuff that makes them want to pull their hair out and smash their zune (like a few people actually did!) so i figured out a way to fix it when all other options failed. unfortunately, it involves taking your zune apart. but hey, if your zune is of no use to you the way it is, what do you have to lose? besides, it's pretty hard to screw anything up taking it apart, it's really not that bad.
ok here is exactly what i did. when you have the case off of it, use your thumb nail to pop open both of the connections where the two ribbons go in, on both sides of the zune. then, first press down the short ribbon's connector on the left side, then press battery ribbon connector on the right side. once you do this, the zune should power up with the loading screen, then go to the main menu (but the d-pad will still be unresponsive for navigating). once you get to the main menu, you need to re-boot it with back+up. the zune will shut down, and begin to power up again. as SOON as the screen lights up, press and hold back, center button, and left all at the same time. this will begin the hard restart.
UPDATE- some people have had luck using back+center+right directional when back center and left does not work.
reboot the zune first if you can, like the zune website tells you to, but if you are un able to reboot, you can press back center left/right as soon as you plug both ribbons back in. also, make sure your battery is pretty well charged before you do the reset, otherwise it will die in the middle of the reset (not a big deal, just a hassle if it dies). also, you cant have it plugged in while you do this.
so once you do the back, center, and left or right combo the screen will say that it's clearing all data and firmware, and it will take a few minutes to clear itself.
once your zune has gone through all the steps to clear it'self, it will prompt you to connect it to your pc. then you can re-install the firmware to the device. and finally you can put all of your content back on it too (which only took me about an hour)
if you want zune.com's directions on the hard reset, you can visit:
http://support.microsoft.com/kb/927001/?sd=zune
ASK ME if you have any questions about any of these steps and i would be more than happy to give a prompt reply and help you out asap! because like you, i was very frustrated when my device was inoperable!