Cant login on desktop manager-ubuntu 5.10
 

Lo guys,tis my 1st 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 runs very fine,but 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.

Thx in advance

Just i wonder if the problem is that ive a x86_64 bit comp and the 5.10 ubuntu that installed is for 32 bits comps only?
Dunno thou cus im totally newb on linux,what you would say about this matter,guys?