Problems with Networkmanager on Gnome after change ISP service

[Eduardo Jauch <eduardo jauch gmail com>]

Hi!

I use Arch Linux with Gnome 3.0.2 and Networkmanager.

Some days ago I changed my ISP service, from ADLS to a fiber one (on the same ISP). 
This required a change on the router that we was using and the new wireless have with a different name and settings than the previously one.

So, after setting the netwrokmaneger through the gnome applet to access the new wireless network, not without some machine freeze during this, I was able to use the new wireless network. 

Almost everything is working. When I start the system it automaticaly start the wireless and I can navigate and all.

But I can't shutdown (or restart) anymore. The system show a bunch of things on the screen (seens to be a kernel panic) and the machine freeze after show the "poweroff" message. 
If I try to disable networkmanager, the machines will eventually freeze (or other weird things) and I will not be able to shutdown or restart.

If I disable the start of the network manager, after I manage to reset the machine using the power buttom, the problems are all gone (but the internet too...)

I have another machine (a notebook), with the same system, that is working properly.

So, I think that can be some problem with my configuration files, but I don't know what are the files where I must look into...

Can someone help me with this?

Thanks in advance :)