If avast finds the executable file for this game suspicious, it will delete it and if you run it, Steam will download it, and avast will delete it again. Steam probably wont let you run the game and the file wont be downloaded, forcing the game into an endless idle update state.

However, you won't have to re-install.
If you are using Windows, press WinKey + R and type the bold text: netsh winsock reset

After you've done this, make sure to restart your computer. Your game will be updated correctly and you may run the game without issues.