Did you try checking if your firewall, router, program or anything else may be somehow interfering with it?
Try stopping all of your programs, stop firewall, if you have a router restart it (reset it if you want to), clean up registries, reinstall VCMP and Vice City.
If after all of this you still find the problem take a basketball bat and beat the sh*t out of your computer.
Make sure that you are using 1.1 version gta-vc.exe