4k Pro Res / DNxHD to MXF Op1a problems

I am converting 4k files in Windows - in media encoder from Pro Res and DNxHD to MXF OP1A - XCAMHD 50 25p

As I have heard this is a great 1920 x 1080 file to use as a proxy

However - its showing up with just a Audio speaker symbol in the output section as you can see in the pic , and is only exporting black screen

Is this because my Graphics card GTX 770 will not support 4k ? or is it because I do not have the correct codec , or is it an issue with windows not being able to
deal with MOV files in this way

If I cannot pursue this can anyone advise me on the best proxy format to edit with in Premiere - downconverting out of 4k ,
I know now that H.254 and MKV are to be avoided as they will slow me down , I want the best possible HD edit friendly version of 4k



https://images.creativecow.net/306863/am.jpg