thanks for quick responses guys,
i havent disconnected any of the cables to pc or monitor, & the pc hasnt moved ( i literally slid the monitor about 12" across the desk ) so i shouldnt have bodged the graphic card or pins, ive unscrewed the connection from both pc & monitor, checked as uve suggested & they all look all ok.
if i disconnect the monitor from the pc, then turn the monitor on, the no signal messsage on the monitor is crystal clear, same as when i ask the monitor to auto set up, it goes perfect then changes back,
Cant check different pc at mo.... im really at a lost as to why it has happened...