Does Cat5 need to be shielded?

I am still having problems with our DSL losing sync. I know signal is strong at NID. But between the NID and the router there is approx 50+ feet of Cat3 cable (looks unshielded).

If I moved the router closer to the NID and then used Cat5 cable to go from the router to the net server, should I use shielded Cat5 or will regular Cat5 be ok?