Since this seems to be an issue a lot of people are having, I've made it super easy to install for anyone.
Here's how you do it:
1. Download Maniafix: Maniafix_1.0.1.zip
2. Extract the zip file in your game folder (eg. where you have ManiaPlanet.exe).
3. Now, instead of using ManiaPlanet.exe to launch the game, use ManiafixLauncher.exe to start the game. (Change your shortcuts for easier access, for example.)
4. Done! Running the game via ManiafixLauncher.exe will fix the freezing issue.
Note: This only works with the latest current version (as of the moment of writing, the build from 2015-06-18).
Note 2: There have been reports of AV software reporting this tool as malware. This is a false positive, it just becomes paranoid when an application tries to mess with the executable memory of another application.
I've also made the source code available on Github.
Let me know if this works for you!
