This is a classic case of an Antivirus\Firewall program that likely just updated itself and is now "protecting" you from Run8. This is beyond our control.

If you are running such a program (Avast, Norton, McAffee, Defender, etc), you will need to go to that program's Settings and Exclude\Unblock V3's exe.

It's also possible (but very rare) that one or more of Run8's DLL files are being quarantined, typically the "Noesis" DLLs that run our menu system, so check for that as well.

Run8 usually doesn't have any trouble with Windows Defender at its normal settings, but if you have your settings set to super-paranoid mode, then you may experience the need to set an Exclusion.

Run8 must have normal read\write access to the Hard Drive, and if you will be using multiplayer, it will need normal send\receive privileges on the internet.