MBP does not wake up after sleep after Mavericks

My 17" MBP is working fine after Mavericks update except for a sporatic wake up problem.

Occasionally, (if I leave the MBP open all night) when I go to wake up the MBP in the morning, nothing happens. Gray screen.

The MBP is connected to a power cord. Battery is charged. Power is flowing from plug.

I have to hold down the power button to shut down, and then again to turn on and everything is fine.

No peripherals attached (execpt iphone cable, which is not connected to the iphone).

Anyone else have this issue or have an idea what's causing it?

Thanks