Yes, not being able to find the a font could cause X to die. You need to find the X config file for the X server and change the font entry to one the system recognizes or exists (or find the fonts you choose and install them).
This is not a very easy task. Font packages are difficult, but you might be able to do it with patience
If you have not installed a lot of custom software, it might easier to do a new Mandrake install and be more conservative about changing default fonts. That might actually be faster than chasing down the font error.
If you are brave and want to try fixing it. Go to the directory /usr/lib/X11 and look the XF86Config.* files and start from that file and directory. Be careful. It is easy to make a mistake here that is hard to correct.