Screen goes blank loading X after upgrading memory

[Marcelino Luna]

I have this strange problem that is driving me nuts.

Since I upgraded my PC (Kudoz 7 motherboard with a memory frequency of 
266 Mhz, an Athlon 1400Mhz and an Nvidia Geforce 4200) with a 512MB 
DDR-333 module (a total of 1GB) Kubuntu seems to start but when the X 
server loads the image on the screen goes blank (the monitor 'says' it 
has no signal). Meanwhile I can hear what seems to be the desktop 
finishing the loading.

The machine seems to work well with Windows and so it does Linux if I 
let it with just 512MB, the old two 256MB modules or the new one.

I've tried to install Kubuntu on another hard disk and the problem arose 
just when I installed the Nvidia drivers.

Any ideas?

Thanks in advance

    //.arce