I have published apk to the Android Market, activated and setup for free for all countries.
I had a similar problem, I explained before but a moderator deleted it.
My app after an update had was available for 0 devices.
Anyway I found the solution for my case, so you can check if it works for you as well.
my mistake was that I included .jar files in order to add some external libraries and not the respective external class folders. When I removed the .jar files and I just added the class folder then devices became over 700 again.
for example I had the facebook API (an old one, not the current) and I had created a jar file out of it in order to include it like this in my app. So when I removed the jar files and added the Facebook API projecy (Project Properties -> Java Build Path -> Projects -> Add..., the app was OK for the android market.
Hope I helped you!