Thank you all for the replies. I am novice in this and you are very helpful.
Basically I am not sure that version 3.3 that I am running now has the right resolution settings as it was in 2.5.8, and USBnetwork didn't seem to work, that's why I was wanting to go back.
My home network in on the same IP range (192.168.2.x), I am not sure if I can use the Kindle network on my PC without disabling the network first. I'll be back soon

LE: The search command didn't work. But I have renamed the file "DISABLED_auto" to "auto" and started the Kindle in USBnetwork mode. I did manage to SU and navigate to the USBnetwork folder and mv the file back to "DISABLED_auto" but I didn't know how to restart the Kindle via su... Managed to restarted hard.
Not elegant, but worked.
Now, what's the location of the fb.modes ?