Can you try to remove your game preferences file and reset your World Of Tanks settings back to default.
To perform this, please perform the following:
Hold the Windows key and press “R”.
In the Run window, type or paste “%APPDATA%\wargaming.net” (without the quotes).
Delete the folder named WorldOfTanks.
Also, this will delete all settings. Including login info.
Afterwards, reinstall the mod pack, and then play a game. See if that fixes it.