| posts: 9,765 | Location: UK
The monitor thinks you are using a digital input (judging by the error), you are connecting with analogue VGA.
You may need to tell the monitor to use analogue (it may be configured only for digital somehow?) or get a digital cable.
If the monitor has a DVI port, get a DVI to DVI cable.
If it has an HDMI port, get a DVI to HDMI cable.
You may as well get a Dual DVI to DUAL DVI cable if the price isnt much different as it may come in handy if you get a 120Hz screen ever.