LCD Monitor problem

Hello,
Please can anyone advise me on my Acer AL1711 problem?
If my monitor is switched on with no input it now cycles through different coloured screens and won't respond to any of the front panel buttons not even to switch off.
It used to flash the message 'Auto setup' then 'No signal' but now just the coloured screens.
If I connect it to the computer and wait until the computer has booted up before switching on it works perfectly and continues to do so whilst there is an input signal to it.
Thanks