I have having the same problem as PoppieJim. I am taking high quality screen shots (jpgs) and importing them into Premier Pro. These are black text on a white background; when I view the jpg files in Photoshop, they are crystal clear.
I have tried setting General Preferences to ‘Default scale to frame size’ on and off with the same results. The preview screen within Premier Pro even looks fuzzy when it is playing, but the resolution looks fine when it is not playing. I have tried every codec available to no avail. I now believe that there is some fundamental setting that I am missing here at the point that the shot are imported. Any other ideas?