problem with start up, nothing displays

Whats the make and model of this computer or alternatively Processor(s) and RAM?

May give us a clue

Try
"unity --reset"
 and tell what happens

I think it may be a driver problem, from a previous helper who asked for the output of:

sudo lshw -C display; lsb_release -a; uname -a; dpkg -l | grep nvidia

It's as follows:

  *-display UNCLAIMED
       description: VGA compatible controller
       product: G92 [GeForce 9800 GT]
       vendor: NVIDIA Corporation
       physical id: 0
       bus info: pci@0000:01:00.0
       version: a2
       width: 64 bits
       clock: 33MHz
       capabilities: pm msi pciexpress vga_controller cap_list
       configuration: latency=0
       resources: memory:fd000000-fdffffff memory:e0000000-efffffff memory:fa000000-fbffffff ioport:dc80(size=128) memory:fea00000-fea1ffff
No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu 12.10
Release: 12.10
Codename: quantal
Linux mano-Dell-DXP051 3.5.0-18-generic #29-Ubuntu SMP Fri Oct 19 10:26:51 UTC 2012 x86_64 x86_64 x86_64 GNU/Linux
ii nvidia-current 304.51.really.304.43-0ubuntu1 amd64 NVIDIA binary Xorg driver, kernel module and VDPAU library
ii nvidia-settings 304.51-0ubuntu2 amd64 Tool for configuring the NVIDIA graphics driver

unity --reset:

RROR: the reset option is now deprecated

I think re-installing graphics drivers through the terminal might solve this but i haven't the slightest clue how.

http://i.imgur.com/U9Tbf.png

I'm not on a laptop? So strange.

I have a similar problem.
can't start Ubuntu, not even in a guest session. When I log in (type password) terminal appears for a second, then I receive the same screen...

fdlruel, try changing into a tty using ctrl+alt+f1 then logging in and typing sudo apt-get install gnome-panel, followed by sudo reboot after that select from the menu gnome classic in the login screen, I had a similar issue a while ago, and the only work around I could find was using a non composited desktop.

Thank you Samuel, it worked!