surface pro 2 - bm hdmi to sdi converters

we had a show with surface pro 2 connected to bm hdmi to sdi mini converters then to the bm 40 x 40 compact videohub router. when we plug in the bm boxes, the surface defaults to a strange rez ( 2560 x 1440? ) on the local display. can't change the ouput to display 1080p 30hz. only allows the choice of 50/59/60 hz. any ideas whats happening here ? we finally by passed the boxes and went straight into spyder x20 with dvi fiber outputting 1080p60. we want to use our bm sdi converters so that we can keep everything hdsdi. anyone see this issue ?

I don't have a surface, but are you in 'Clone' mode or extended desktop? If it thinks you are in Clone mode then it usually defaults to the size of the internal screen and if that screen doesn't support 30p then it won't allow you to take it down that far