Hello guys if you want a challenge with your knowledge in hardware then read this up! 
I got this monitor two days ago and I have so many problems with it. Anyway I tried a lot of things to fix this monitor, but this error is something beyond. Here we go.
I have already one LG monitor which I use for work and I decided to get this HP E231 one as my second. I connected it and it worked like half hour or less; black screen. This was on DP and it could sometimes come back from black status but on DVI/VGA couldn't.
So my monitor stays shut down and nothing works on it but my LG is okay. The only thing to get HP back to work is if I unplug/plug power cable. So I did that and this is how I fight with this problem.
After few hours of fighting, I did get random black screen then colors; red-green-blue, etc. Checked Internet found out option "Burn In" so I turned it off from Factory menu. No more disco style, but still this black screen. Next I tried all type of cables:
- 4 different power supply of my own
- VGA, DVI, DP ports all of them changed and tested still the same error
After that I decided to switch it to integrated GPU, maybe my Asus 270 is making problems, but that was not an answer. Tried working out on my server machine with Nvidia GPU, nope. Switched to VGA port with my laptop, again the same thing. Black screen. Funny thing is, it is not only black sometimes it stay like that even if you TURN OFF the whole PC and it will shine. 
Only thing to remove that is to unplug/plug in power cable.
Best thing now! Today, I tried lot of options in menu and not sure what happened but my monitor blocked commands on panel, can't turn it off or anything. I went to work, got back home; bam 9 hours working and it is still on. I did know if I plugged cables out and back that it will work with menu but again it will go to black screen.
tl;dr
Monitor goes black in 30min work, sometimes it works 9hours but menu commands doesn't.
I got two short clips (my camera on phone is broken, bad compling with android )
Disco clip, potato quality as it finest:
https://www.dropbox.com/s/3kl845rk6vno8us/video-1426806189655-V.rar?dl=0
This is menu one, when nothing worked but monitor stayed up to 9hours:
https://www.dropbox.com/s/8uilzi7i9jh7xi6/video-1426804087219-V.rar?dl=0
Sorry for long text and english mistakes it is my fourth language. Thanks.