This really should be in the Medium Format area - you'll find more help there.
Having said that, what does the seller say about this? How long has the camera been sitting around before you purchased it?
What model battery are you using, is it fully charged, and have you recharged it fully? Can you tether to a computer using FW800? It may want to be plugged in and charged for a while - there's a rear curtain that's on the body that protects the sensor and that may be having issues. Have you pulled the back off the body & looked at the contacts?
What lens are you using, and was it part of a kit from the seller, or was it acquired separately? When you're shooting these images, are you doing it hand held or on a tripod? Does it happen across multiple lenses, or do you only have the 1 currently? Do you get the same visual when the camera is in vertical orientation as in horizontal?
-Joe