My screen is jumping up and down like a yo-yo, anyone got any ideas why this might be?
Do you think its more likely to be a problem with the moniter rather than the computer.
Any advice appreciated.
Thanx in advance.
Bad connection? Bad monitor? You tried turning your monitor off and back on? Do you have an electromagnet suspended above your desk? 
Couple more details?
Turn the Monitor Off
Wait for the earthquake to subside
Turn the Monitor back on again
Do you have a fan or any other device that might emit EM radiation? If so move the offending device away from the monitor and see if the problem subsides.
Next time, don’t buy a computer desk from Rubbermaid.
Unplug it from wall for a minute & plug back in. A full minute, not ten seconds. See what that does.
a) Where are your speakers? Did you put new heavy-duty speakers in the vicinity of your monitor recently? How about OTHER things with big honkin’ magnets in them? (More likely to cause funny colored blotches and spots than jumping-like-a-yo-yo though…)
b) Check your monitor cable connections, and if your monitor port isn’t an intrinsic part of the motherboard or something, check the connection of video card to motherboard.
c) Did you have the same computer, monitor, and cables working just fine until recently when it started jumping up and down like a yo-yo? Or are you hooking up a new monitor to your old computer, or hooking new monitor and new compute for the first time here?
d) Do you have another monitor you can hook up to same computer? (If so, does problem disappear?) How about another computer you can hook up to same monitor? (If so, does problem disappear?) As much as possible do these swap-outs in such a way that all components are located in same place as currently glitchy system.
e) Look across the room at your bookshelves or window curtains or kitchen drawers or something. Are THEY jumping up and down like a yo-yo? Hey, just asking…
Is the computer/monitor plugged in to a circuit (not a wall jack, but a circuit) shared by other appliances? In my old apartment, the living room and kitchen shared a wall and wiring, and turning on the microwave would make the monitor image look as though it was vibrating.
I know this sounds stupid, but does your monitor have V-Hold on it? Probably not if it was made in the last few decades. How about trying a DeGauss?