Weird issue and Can't open display

[tsuraan]

I'm having this really bizarre and annoying problem lately with my X
install (running KDE4.6 on top).  I'll be using my computer without
problems, and then I will be unable to open any new windows.  If I go
into an already-open terminal and attempt to run xeyes (or anything
else), I get this message:

tsuraan at localhost ~ $ xeyes
No protocol specified
Error: Can't open display: :0

So, somehow I'm in a running X environment, but I'm unable to connect
to it.  The system was happy, and then something unknown happened, and
it became not happy.  I unfortunately don't know enough about X to be
able to say much more, so I'm hoping somebody can give me some
troubleshooting tips.  In my home directory, I have a .Xauthority file
that is readable by me, and if I run xauth (firing up the program is
really all I know how to do) it says it's reading from
/tmp/kde-tsuraan/xauth-1000-_0, which is a different file but has the
same contents as the one in my home directory.  The two files do have
different dates though, and the one in my home dir actually pre-dates
the boot time of my computer.  I'm not sure what exactly that implies.

A random selection of installed software versions follows:
libdrm-2.4.23
mesa-7.10.1
xorg-server-1.9.4
xf86-video-intel-2.14.0

I'm really hoping somebody can give me some tips to figure out what's
going on.  My current remedy is to re-start my X session, which is a
bit of a pain.  Something less invasive would be nice, or if I could
actually track down what is causing my X to stop allowing new windows
and kill it, that would be ideal.