It looks to me that nouveau driver is not for your nvidia card model. You can do this if you want:
Download the nvidia driver for your card at the nvidia website, do it accordingly.
Make sure you have the linux headers install as well as "gcc" and "make", before installing the driver. This, to avoid any problem.
Enter the safe mode or text mode, uninstall the nouveau driver and blacklist it in the modprobe blacklist.conf (/etc/modprobe.d/blacklist.conf, just type "blacklist nouveau", save it and exit) install the nvidia driver (previously downloaded from nvidia website and according to your card model), just follow the instructions.
Startx the X's (startx) or just reboot (reboot) at prompt.
If you startx and see some problems, you might want to do this:
modprobe -r nouveau
If you just reboot, at startup it will load all sistem with new nvidia driver.
If you are not familiar with linux, just reboot.
Why install nvidia driver?
1. Avoid error messages.
2. 3D support.
3. If you want to use compiz, emerald, desktop special effects.
If you want just to pentest, leave it the way it works for you.