I will assume that you're trying to startx
from a text mode runlevel. If this isn't the case, then you might want to try.
If you hit Ctrl-Alt-F1 at the blank screen, do you get a prompt back?
If so, check the output of dmesg
for a kernel oops. If you're getting one, then try the patches at minion.de (or just bunzip2 the 5328 patch, remove everything except the hunk that patches os-registry.c, near line 618, and apply just that hunk).