viewing live video through a monitor

Hi Guys, I'm new to this forum and wonder if anyone can help me.

I have a D5100, if I hook it up to a monitor with either a HDMI or AV, I can see live view on the monitor but if I start recording the monitor screen goes blank, this only happens when the camera is set to record at it's 2 top highest quality settings and at 25fps, if the camera is set below these qualities then the live stream will work when recording, anybody know why this is, and how to get around it?

Many thanks.

First thought that comes to mind is that the processor is not capable of streaming the high quality video and processing the recording at the same time, but if you downgrade the quality the processor is not working as hard and can therefore stream externally.

This might not be the reason, but it certainly sounds like a good one

Hi Sam, those were my thoughts as well, the thing is I need to record at highest quality (from a remote quad copter) so I need to watch on a monitor vie a down link, but the monitor doesn't have to be at high quality, so I'm stuck.