I am really at a loss. I copied your link and the theme installed fine. I downloaded the file to my desktop, replaced the one background image with one of my own (173x173 png), re-zipped keeping the same folder integrity, and still got the corrupt message. I uploaded to a different server (this time skydrive) and downloaded from there. Still no dice.
On different note, I did use a picture from my saved photos on the phone and created a phone shortcut. It seemed to work fine. Once I tried to enter your app again it would crash. I restarted the phone and tried again but could not get back into the app. I uninstalled and re-installed. It worked. I installed the sample file that you asked me to and it installed the metro theme. When I tried to enter your app again, it crashed.
I am running a Samsung Focus, v1.3.