Strange X freezes, system otherwise responsive

I'm not quite sure where to submit this query, but I'll start here. Up
until recently, I've had a system running X continually for weeks at a
time with very few interruptions. I'm using the newest nVidia drivers
with an MSI GeForce 4 Ti4200. The problem is that after a period of use
(seemingly random), X will just freeze. I can't switch to a virtual
terminal, and alt-ctrl-backspace causes a monitor diagnostic that I see
when the monitor isn't receiving a signal from the rest of the machine.
Occasionally, the text around the cursor will blur, but not entirely --
either the upper or lower baseline. I haven't yet noticed this happen in
any window manager other than Enlightenment, but I'm hard-pressed to
believe that it's E's fault because I've used the same package -- and
configuration -- for months (since I first built it almost a year ago).
The curious thing about this freeze is that the rest of the system is
still perfectly responsive: I can access the machine via SSH and kill X
(which causes strange horizontal lines to appear on the screen, very
similar to what I saw with the previous version of the nVidia X driver,
but not quite the same -- there's more of them), and then restart X and
continue using the system as normal. Another curios aspect of this
freeze is that xmms continues to play music until it advances to a new
song. If I'm streaming something, it goes on indefinitely. And no, 
NumLock seems to have nothing to do with it. The freeze occurs both 
with and without it. I'd upgrade my E, but that seems to break some 
things like iconifying a window and being able to alt-tab to it on 
another virtual desktop -- a feature which I use very often. 
Thanks in advance for any assistance with this. I'd be very pleased 
to provide any other information.

-- 
I abhor a system designed for the "user", if that word is a coded
pejorative meaning "stupid and unsophisticated".  -- Ken Thompson