OK everything fixed
I was right the first time, the GLX screensavers needed the GLX module loaded to work
so I installed the new nvidia driver and added the glx module in XFreeconfig file...
now every work
by the way I had a problem with the nvidia driver, the X server failed to start, this problem was caused by the order the module were loaded, (I founded the solution in the nvidia forum) so to force the nvidia driver to load I added a new the line in the /etc/modprob.preloads. This line simply reports the driver that needs to be preloaded, in this case nvidia
thats it
D.