It sounds like the dewberry vine, which invades my yard, too.

Here is a link that might be useful: Dewberry vine

I don't know the name of it but it sounds like a vine we have here. You can spray all the round-up you can get your hands on but unless you remove the root it will always come back and if not removed it will kill the plant. If it is what I am thinking the roots will have like little potatoes or knots. Good luck with your viscious vine.