a quick work around to get the 1.6.4 version to work was going to Android System Settings > Apps > FrostWire and then manually give FrostWire storage permissions.
On this release (just built for you guys)
https://github.com/frostwire/frostwire-android/releases/tag/frostwire-1.6.5-b205
We have integated the new Android 6 permissions framework and you should be asked the first time you run FrostWire for storage permissions.
Other than that we fixed a lot of stuff and improved subtle user experience details.
Please let us know how the download experience is, we heard Android 6 might put background servicds to sleep to save battery (while at the same time it encrypts all your stored files, probably very battery intensive...)
We havent been able to test long downloads much as we had to code the release on a very slow emulator.
let us know how it goes.