Thant's an odd behavior. Have you checked the PSU? Is its power output correct? Are you using the PSU included in the Galileo or any other PSU?
Are you powering external circuitry from your board? If the external circuitry consumes too much power it may cause this behavior on the Galileo. If that's the case, then I'd suggest you to use a separate power supply for the external circuitry, it may prevent this issue.
It's the second day I use the Galileo gen2 board, and I found the problem after lunch when I pluge in the power. The power out is correct. I use the PSU included in the Galileo and a separate power supply for the external circuitry. But it still can't run simetimes. The PSU is a new one and my friends can use it on another Galileo2 board.