My advice for you would be to create a new user account on your computer.
Go to Control Panel -> User Accounts -> Manage Another Account -> Create New Account -> Make it Administrator and play GunZ from this account.
It could be because a certain background process is blocking something on your computer. Making a new account might fix it because it means that you don't have all the background processes.
Go to Control Panel -> User Accounts -> Manage Another Account -> Create New Account -> Make it Administrator and play GunZ from this account.
It could be because a certain background process is blocking something on your computer. Making a new account might fix it because it means that you don't have all the background processes.