I have Raspberry 2 model B+ which I tried installing RasPlex, two times. At first I used dd on Linux to write imege to SD card. Second time I used oficcial installer. The image is 1.8 for Raspberry 2.
It does have Hifiberry DAC+ attached.
It doesn't boot.
Previously I used OpenElec on exactly the same hardware with no problems.
Update: tried 1.6.2 image with same result.
Verify your power supply is at least 2amp and you are using a good quality usb cable.
I think I recalled downloading the wrong image version once and it did this. Verify you are using the correct build for your hardware
the square rainbow on the top right means that the power supply its too low, if you see it big in the middle of the screen means that your rpi isnt booting the image. I guess its the latest case, just reflash it with a clean image or try a new micro sd