Cannot join servers with mods (game window never starting)
Stay in the main menu or close your game if you're already stuck without the game window opened.
Open a command prompt (cmd) in Windows and paste this command (right click) rmdir /s /q %localappdata%\Plutonium\storage\iw5\mods then press Enter
Until Plutonium fixes that issue you'll have to do that when the issue occurs.