Dell monitor randomly goes blank on Mac mini I have a Mini late 2012 (i5 16GB RAM). It was running Mavericks and now running the Yosemite Beta. A Dell U2414H and an older Dell E207WP

My problems is:

My Dell U2414H randomly says there is no signal and goes black. The only way to get it back is to reboot my Mac.  This happens randomly, it could happen 10 times in one hour or once in 2 days. I have the monitor connected via Display Port to my Mac's Thunderbolt connection. My other monitor (E207WP) is connected via HDMI to DVI (woks fine).

This problem started on Mavericks and continued to Yosemite. I have performed clean installations of each but the problem persists. I do not have any other computers available to test the monitor on.

I have ordered a few Display Port and HDMI cables from Amazon hoping that will help.

If anyone has any ideas I would really appreciate the help. Restarting my Mac all the time is killing my productivity.
Maybe the problem is caused by overheating.
When I put a pot filled with cold water on top of the mac mini, the blank screen problem occurs less often.