Now that I've got my window manager nightmare in Redhat 9 fixed, now there's another problem:
I've got a strange redraw problem that appears related to my mouse pointer… anytime I click on any UI item – OP tiles, pull-down menus, buttons, and text fields – there's some kind of redraw glitch where my mouse pointer is, it's in the shape of what looks like a 32 pixel square. Here's what happens:
1. I click on the viewport's camera view pop-up menu, and the menu pops up, but the square area where my mouse is gets redrawn with the original graphics of the menu, before it was popped up (does that make sense?). If I force the window to redraw by resizing the panel or whatever, then everything looks normal again. Unfortunately I can't seem to get a screen capture of it.
2. I click on a text field to make a change, and what I type in doesn't appear, instead all I see is the hilighted text field, with the previously existing value, and some munged stuff around it. I hit enter to complete my entry and it still appears screwy. Then if I force a redraw, it looks right again.
This is happening EVERYWHERE in the interface, and it's a mess! It's also the same in Houdini 5.5 and 6. On the other hand, the 3D viewport is perfectly fine, no troubles there. I'm using an Nvidia Quadro card with the latest drivers, and I've tried tweaking all the houdini environment variables I can think of, and tried different NVidia settings too (Hardware cursor, software cursor, no difference). Has anyone encountered anything like this before? I'm guessing it's a driver setting, but I can't seem to track it down.

RedHat 9
Sawfish window manager
Nvidia Quadro, drivers 1.0-4363
Houdini 5.5, Houdini 6

Many many thanks to anyone who can help!
–Jason Simmons

I finally got my graphics problem fixed, and thought I'd just post my results for the record:

I tried changing window managers, tried switching from Gnome to KDE, tried updating my NVidia drivers and tweaking all imaginable settings, and none of that helped. What finally worked was getting rid of RedHat 9 and installing RedHat 8 instead… must be something with the newest version of XFree86 causing my troubles. All's well now that I'm using RH8.