Tvheadend

You don't say what you're installing it onto - but that sounds like a repository problem. 4.1.x is part of the unstable branch, versus 4.0.x which is stable.

Check your repositories. If you're running a Debian platform, try sudo apt-cache polocy tvheadend and it'll tell you where it's coming from.

EDIT

Just read your question properly... you're not after stable, you're after the latest nightly. The same statement applies, though: check where your package is coming from, as 4.1.560 should be available from the unstable repo.