Dell P791 monitor flickering problem

I have a Dell P791 CRT monitor that has developed a very annoying flicker.  Rather than normal vertical flicker associated with refresh rates it is shifting from left to right with the screen content being compressed and distorted in the process.
I have trield all the refresh rates and resolutions without success.  Followed all the points in the knowledge base including location, alternative power supply, rf devices, kinks in the cable, turning the monitor 90 degrees, change and update drivers etc.
Normally I have it plugged into my base station, but I have tried it directly on the laptop with the same result.  I have also tried another dell laptop, and two other desktops (not Dell) with the same problem.  It is not Windows either as the problem is exhibited under Linux as well.
I can only assume that the monitor is now faulty but I just wanted to check I have not overlooked anything
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