I can't start Gnome as normal user

[Francesco]

Hi,

I upgraded my debian distribution from Sarge stable to testing and
everything works. Then I did it again and the process went fine. But
this time I am no more able to start my X server. I commonly use gnome
(now 2.14) and my xorg.conf works well. I read the log file, but any
errors are reported.
The exact problem is as follows: I give the command "startx" and the X
server tries to start. I can see the first screen and after that my
system blocks completely. I can't neither shift from one console to
another. I am obliged to shut off the computer.
I noticed that gnome starts if I log in as root user, while, being
normal user, I am able to start Kde.
I really can't understand where is the problem.
I hope you can help me.
Thank you very much,
Diseconomia