- Check your power supply, that it can sustain at least 1A-1.5A continuously. Some are marked by peak performance.
- Check your cables. A cable that has a breach inside can cause all kind of funny effects. Does your board reboot when you wave the cable?
- Check that you put your SD card in the slot on the CPU module, not in the slot on the larger PCB. On the quad the slot is under the heatsink.
- Check your SD card. Sometimes they can have bad blocks.
- Check that your monitor is a real HDMI monitor, using a HDMI cable. Some DVI to HDMI converters are known to cause display troubles.
If this did not help, go through the items / troubleshooting hints in the more thorough list (sorry about the mess)