PI hangs or network hangs?

[Fabio72]

Since I started to use raspi with xbian I faced, time to time, the same problem.
Xbian works fine for days or weeks then suddenly, after an AC failure or some other problem, it start freezing after 30 or less minutes of use, with no errors in any log.
Then I restore last backup without solving the problem.
Every single time I have to try many backup restores to get it working again. Usually I have to restore a much older backup.

I switched to nfs root but this issue is always present.

I changed hardware (B and B+, SD card, PSU) with no luck.

My Xbian is up for months, survives firmware and kernel updates and reboots. Then suddenly it starts freezing again. Until I restore a month old backup.

I just read this article
https://raspberrypispot.wordpress.com/2013/07/08/wifi-and-ethernet-dropout-problems-in-raspberry-pi/
“FIQ interrupt not triggering IRQ interrupt causing USB to dropout”
I tried on my system

Terminal

root@xbian /home/xbian/.kodi/temp # cat /sys/devices/platform/bcm2708_usb/regoffset
0xffffffff
root@xbian /home/xbian/.kodi/temp # cat /sys/devices/platform/bcm2708_usb/regvalue
invalid offset

And then

Terminal

root@xbian /home/xbian/.kodi/temp/check_lan # echo 08 > /sys/devices/platform/bcm2708_usb/regoffset
root@xbian /home/xbian/.kodi/temp/check_lan # cat /sys/devices/platform/bcm2708_usb/regvalue
Reg@0x000008 = 0x00000031
root@xbian /home/xbian/.kodi/temp/check_lan # echo 0x31 > /sys/devices/platform/bcm2708_usb/regvalue
root@xbian /home/xbian/.kodi/temp/check_lan # cat /sys/devices/platform/bcm2708_usb/regvalue
Reg@0x000008 = 0x00000031

Maybe this is the problem: network stop answering but raspi is not freezed. Having root nfs, nothing is written to the logs.
Then I remove the power plug to restart the PI and no trace of what happened remains in logs.

Now I'm trying the script in the article