6970 3 monitors

[mena5741]

hi

i use microsoft flight simulator fx win 7 64
i have saphir 6970 ,3 monitors lg ips236 23" 1920X1080,
two dvi ( single), one dvi (dual), active adapter (with usb) mini dp to dvi
the dual dvi is connected to the mini dp
most of the time i get a massage that it dos'nt recognize the dp connection
is the fact that i use 2 type of dvi cables can couse to this ?
mabye the usb port ?

thanks for help
Menachem