My 3008WFP has started freezing and doing this recently when using my PS4 via the HDMI input. The area around the border continues to function normally, but clearly it's unusable. I called Dell support but it just hung up on me.
* Turn the 10 year old 3008WFP off
* Disconnect every cable from the 3008WFP including the power cable
* Press and hold in the 3008WFP power button for 8 seconds
* Reconnect only the power cable to the 3008WFP
* Turn the 3008WFP on. The floating "No cable" dialog box should appear on screen against a black background. How does it look?
Gave it a shot. Result was a black screen with a blue bar at the top. No cable message.
Pressing the panel buttons made the blue bar go away, and made the screen two different shades of black (barely discernible).
Some internal component has failed. Unknown as to which one because Dell does not repair monitors.