I have a Raspberry Pi 2 running for quite some time now with the default
raspbian image from the raspberry homepage. I have
tightvncserver set up which was also working like a charm until I mistakenly powered down the raspberry.
After the reboot vnc sessions only show me a black & white "rasterized" screen whilst the X server seems to be running fine since I see the usual desktop when connection over HDMI.
I've already tried to simply uninstall & reinstall
tightvncserver which didn't change a thing. Also subsequent reboots didn't work.
I somehow messed up some permissions in my home folder. Among others, the file /home/user/.vnc/xstartup didn't have the execute permissions anymore set and therefore didn't start correctly...