Dual receiver reception issues

[nhchamp186]

I have a dual lnb dish and 2 receivers. When I hook up only 1 receiver it works fine, when I try to connect the second receiver, (seperate coax) it only gets reception on a couple of transducers. It doesn't matter which receiver I try, it has the same problem. If I disconnect either one of the receivers, the other one will then work fine. How can 2 seperate cables connected to a dual lnb dish effect each other?? I have had this same set up for a few years and it always worked fine... I use it during football season for Sunday ticket and found this problem when I fired it up a couple weeks ago. Is is possible that my lnb is bad???? What else could be causing my signal loss when 2 receivers are connected???

Thanks,