With VSS error codes it is always going to be a bit of a mystery I'm afraid. Try cutting and pasting the command Ant was trying to run in to a command prompt and running it, see what happens. You might ge tmore information.
Generally VSS errors boil down to invalid file paths or invalid file permissions. VSS itself is nothing more than a few extension on the basic windows file system after all. Check you can access you VSS "database" - see if //192.168.130.20/RallyTTPro is shared as you believe it is and it is accessable from the machine you run this on for example.