My RPi is working fine and automatically connecting to wifi when powered from USB but when I try to power it from a regulated 5V supply on the extension headers I can see that it goes on but then short after a while the wifi dongle's light goes off and I never get a chance to even ssh in. When I powered it from usb again it works completely fine. Any idea what could be causing it and what I can do about it?
PS. The 5V is regulated from a 12V open frame power supply and seems to be a very solid supply.