I have just installed CentOS 5.7 x86_64 on a new computer. The installation went on without any issues. But, after it finnished, the machine started to show an awkward behaviour: it restarts every time it tries to boot.

It happens after all the services have been started. The screen just goes black and it shows an error message from the monitor: Input not supported. And then it reboots.

I took a look at the logs, but I couldn't manage to find anything.

Any help?

Update

Before doing the hardware diagnosis, as pointed out, I decided to make some tests.

First, I changed the runlevel to 3, adding the 3 parameter at the end of the kernel command. Then, after logging in in text mode, I checked the xorg.conf file out for some problems regarding the screen resolution. There was nothing unexpected set. Well, if there had to be a problem with it, I couldn't start the X server at the command line, right? So, I typed startx and Gnome started! So, probably, it's not an issue with the screen resolution, I suppose.

Then I selected the Log Out root... Gnome menu option and something odd happened: the screen went black, the Input not supported monitor error message was displayed and the system rebooted. Yes, the same problem I was having while trying to boot!

After that, I decided to try yet another test: I removed the rhgb quiet parameters from the kernel command to see if some error would show up. Well, to my surprise, the boot went on without problems! The Gnome login screen showed up, I logged in and the session started. But then I selected the Shut Down... menu option and guess what? Same problem: black screen, same monitor error and the system rebooted. Yes, it rebooted, it did not shut down.

I repeated both of the tests and the behaviours were the same. I really don't know what's going on. It seems to be an issue regarding the changing of the screen mode or something like that.

Any ideas? Could this be a hardware problem? Or does it seem to be something regarding the system configuration?