My TV says it's receiving a 3840 x 2160 signal. I tried rebooting, deleting cash and reinstalling.
How else can I verify the signal?Added (15.01.2015, 02:05)
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It was my text size adjustment.
I changed the setting in the windows 7 control panel to enlarge text to 'large'. I changed it back to default and that corrected the problem.
Go figure.