Cant login on desktop gnome-ubuntu 5.10

[metamorphics]

Lo guys,tis my 2nd thread here and i wish that u can help me cus im very very dissapointed,installing and reinstalling ubuntu 5.10 all the time,even the installation seems fine.
My problem is:I cant login to desktop,while ubuntu runs fine till appears the brown login screen.When i type the first letter of my username,then system freezes totally,nothing works,nor ctrl+alt+space or ctrl+alt+del,stuck and again stuck!!
Tis shame for me but i cant find the solution,so i install and reinstall ubuntu 5.10 all the time,hoping that will fix the problem,cus im totally newbie on Linux,tis my 1st distro that i try
to install.
My specs are:

CPU DualCore Intel Pentium D 830,3000MHz(14x214)
Motherboard Gigabyte GA-81945PL-G
Memory 1024MB(DDR2-533 DDR2 SDRAM)
Bios type Award Modular(10/25/05)
Video adapter Nvidia Geforce 6600 LE (256MB)
3D Accelerator Nvidia GEforce 6600 LE PCI-E
Monitor Eizo Nanao L768 (Analog) [19" LCD]

I cant understand this:ive almost install all perfectly and ubuntu 5.10 runs very fine,but when it shows the login screen and i type the 1st letter of my username,then stuck,freezes for ever!
Can you help me guys?You r experienced users and u know many.How i can fix this display manager problem?my display manager is Gnome,installed fine as i think.Where should i investigate this major problem for me?

Thx in advance

[engineuity]

instead of typing anything when the login screen comes up, try doing a ctrl-alt-f1. This will bring you to a console login. If you can login here, then I am assuming it is an X problem. If not, there may be some hardware conflicts? If you can, try to start up in the recovery mode, the second option from the grub menu. This should just run the basics to get your system up. You will not be able to give the root password because there is none, so just continue with the boot. Do the ctrl-alt-f1 to bring yourself to a console and try to log in.

So, If your able to log in on the console, i suggest checking some of your logs. Ex: check the file /var/log/<i think xorg.0.log> I dont know your linux familiarity, so if you need help with the commands, just post what you need. If not, theres no sense telling you things you probably already know.