Monitor switching off

[wnm0]

My monitor switches off if I even slightly move the base unit, I changed the svga cable and it was still doing it so I tried my old monitor with a fixed vga cable and it will still switch off say no signal, I have checked the graphics card and it is fixed in the pci slot with no movement, I am not sure what to check next so any help you can offer would be great.
Thanks in advance for your time and support..
Regards, Wayne...
p:s forgot to say I have a dvi to svga dongle fitted could it be that?

 

[wnm0]

No body have any ideas? even just a slight idea of what it could be would help lol..Thank you..

 

[Kelt]

No body have any ideas? even just a slight idea of what it could be would help lol..Thank you..

I'd try and isolate where the problem is, i.e does it switch off if you move the cable at the back of the monitor, or at the graphics card end.