I shot a film usinng the Canon C300 recording 50 Mbps MXF MPEG 2 files. When I import them into Adobe Premiere CC all playback shows a white screen (not rendering). In Adobe CS6 it works perfectly. I just got the Adobe CC trial to see if it is worth paying for and to try out editing in it but this problem won't let me see my videos. Audio works fine, however.
I suspect you may be having issues with activation. Sign out of Creative Cloud, and then sign back in. See if you are able to import your files after that.
More trouble shooting steps are found in this doc: http://helpx.adobe.com/x-productkb/policy-pricing/activation-network-i ssues.html