wifi goes down after a while

[QuadCorei8085]

Same problem here.
My config is:
- rev2 PI 512Mb
- some TPLink Wifi dongle (8192cu)
- 8gb SDCard
- 160Gb usb hdd (system is moved using xbian copy)

Previously i used XBIAN Beta2 and upgraded it to RC2 (using a the SDCard as locked, just for kernel). Wifi worked fine without problem.
A week or two ago I had a power outage and of course it crashed my system (blinking cursos problem) as it did it for many times now.

So reinstalled the XBIAN but from installer I choosed RC2, ever since I'm experiencing this wifi standby thing.

After bootup transmission's web ui and ssh is available. But after a while the PI is no longer available, no ping response or SSH,
however XBIAN is still running and on system settings it sais the correct DHCP (statically) given IP address. Furthermore the ifconfig from console gives the same result. Also ping from RPi doesnt give any result all packet is lost.

But yesterday evening I experienced some strangeness that could give some info for experts: if I leave an open SSH session (with "top" running) or
leave the browser on transmission gui the connection persists. The RPi only looses the connection after I terminate the open connections to it, and not right away but some time later (didnt measure the time).

As previously stated here it might be a standby issue, seems when the wifi is no longer needed the RPi carelessly shuts it down..

Any idead why this is happening? What changed in RC2 in wifi settings?

ps: power is not an issue here, the RPi is supplied with a 5V/5A regulator through the USB hub (the interface USB is directly connected to input 5V). But just to rule out the power supply case I connected the offical RPi adater to the micro USB port also to give "more" power to PI just in case. The wifi had still shut down.