I also have this problem, not from this site, but I bought OWC dual drive kits. Also I have Samsung SSD 840, not pro. Mac mini doesn't recognize the 840. Did all kinds of stuff, tried different SSD (OCZ Vertex 2 -> didn't work either), tried different slot, reseated the cable, didn't work. Because other drives didn't work, I suspect this is problem of cable at the moment.