hi) got an issue connecting second monitor to mac mini mc816

connecting one via hdmi is totally ok

but when i connect the other one via 'mini displayport to hdmi' + 'hdmi to dvi' adapter its blinkng/flashing/flickering every ~2 minutes

it also refuses to wake up after sleep

one of the monitors have the built-in speakers and if i connect this monitor via mini displayport i also hear a 'punch' from the speakers

i got this second-hand mac mini a couple of months ago and the problem apperared yesterday

any thoughts?

also ordered a new 'mini displayport to dvi' cable on ebay