Just put a set of Rotosound Swing 66's on my Musicman Sterling Ray 34 bass having previously adorned it with D'adarrio. Whilst bringing the D string up to the correct tension it snapped about an inch from the ferrule! No issues with the other 3 strings, all in tune.
Contact Rotosound UK http://www.rotosound.com and spoke with their customer service to explain my dilemma, and the guy on the end of the phone turns out to be very understanding, apologices for the breakage and immediately sends out a replacement D string (first class) at no cost to myself.
If nothing else Rotosound deserves a mention on this and similar forums for excellent customer service.