Can't export Still Images - Getting a Black box

Hi,
I have tried uninstalling and reinstalling 15.4 here is my issue..
i moved from 14 to 15.2 and lost the ability to export still after grabbing still. I would export a black box.
I upgraded to 15.4 and the first time or two I used it, I'm pretty sure it worked. I then grabbed a bunch of stills from a long project and now none of them will export correctly. I have tried exporting to different folders different drives and have no luck. Anyone having this same issue?
I love DR btw so happy to be learning this powerful program.
Thanks

I have resolved this issue.
FTR I checked disk permissions and i "blew-out the prefs for I/O and drives, put the Capture/Scratch drive and path in there, and make sure the permissions are correct. You will most likely have to reboot/relaunch in order for this to take effect." - thanks Marc!