Try maybe something like
- Uninstall all MTA files and search for ones that could be remaining and delete them.
- Uninstall VC and search for files which could still remaining on your computer.
- Install VC
- Play to the first save point which i usually do
- Restart computer
- Install MTA and play.
This is normally what i do and helps me sometimes, most of my problems are solved by just deleting old files from the ones you uninstalled. Firewall, Router problems etc i wouldnt know.