I recently restrung my SX SJB 62 with Rotosound Swing 66s, the first time changing the strings since I got it. The next day, it was quite out of tune, so I started tuning it, but once I got to about Db or C on the D string it snapped! So I go out and buy another string, same thing happens. I now have another string on it about C, but Im afraid to tune it more in fear of it breaking again, because I can feel it getting tight. As I said, the first time it was a Rotosound, then a D'Arddio, now a Ernie Ball, so it must be the bass. Anyone ever exprience anything like this before? Know what might be wrong?