Try something as minimal as possible. First:
sudo apt-get install xterm
Now create an xinitrc file for your current user:
echo '#!/bin/sh' > ~/.xinitrc
echo xterm >> ~/.xinitrc
chmod 755 ~/.xinitrc
Check that it looks like the below w/
Now, as the same user, try
startx. You should end up with a plain black screen, an
X shaped mouse cursor, and a (very primitive looking) black on white xterm window.
This is just to check if it is not something weird with the higher level GUI stuff. You can exit w/ ctrl-alt-backspace.
In any case, you could also try adding this to
/boot/config.txt and rebooting:
I'm presuming this is an HDMI monitor. Comment out any other
gpu_ lines by adding an
# to the beginning.
If that works, have a look at the documentation for
hdmi_boost and experiment. You'll have to remove
hdmi_safe first -- there is documentation for that on the same page -- and possibly experiment with setting some of the things that sets (e.g.,