Arduino Yun disconects from the PC after hours of PC inactivty.

I have installed my Yun as Client and connected to a Router then to my PC. A Webcam is connected to Yun and all is working fine,
In teh evening I disconnect the PC and in the morning I am no longer able to see my Yun even if the Router is UP and running.
Have somebody experienced the same trouble?
Luigidv

Is the yun connected via wifi? How do you power it?

It's normally and constantly polugged.
I've upgraded it too.
Luigidv

I miss how do you power it: do you have an external power supply or is it plugged to your computer?