Haupage 150 and 500, but only 2 out of the three work

I have a vista premium system set up, have a Haupage 150MCE (1 tuner) and a Haupage 500MCE (2 tuners). very simply, only 2 out of the three tuners are working. I did further tests by disconnecting the coax and found that 1 tuner is working on one card and the other tuner is on the other card. tested them further individually, both work on their own with the correct amount of tuners (500 had 2). Whats up? Do I have to buy another 500 to get 4 tuners?