xfce, Apple X11, and mouse emulation

[Fred and Margot Dushin]

I've built fresh copies of xfce4 on a macbook and MDD G4, and I get  
the same behavior:

I can get XFCE to come up under Apple's X11 (startxfce4 in  
~/.xinitrc), but there seems to be something messed up with button  
clicks/mapping -- I can't get XFCE to respect any button clicks,  
either in the panel, or on the desktop.

If I turn off "Emulate three button mouse" in X11 | Preferences...,  
then I need to use the option key to get the WM to listen to left  
clicks.  With the option key down, the WM will also honor right  
clicks on the mouse (logitech and Dell 3 button mice tested).  I need  
to use the command key to get the WM to honor window closes (left  
click on X button).

It's also a bit strange that if I use key combinations a number of  
times on the same widget (e.g., settings icon in panel), I no longer  
need to use the option key.  The WM/server appears to "learn".  Some  
dialogs in Xfce require no modifiers.  Strange.

As I said, I can reproduce on an intel and ppc box.  Anyone else see  
this?  Or know anything about mouse button mappings in X11?

(Trying to reproduce in Gnome, but I'm currently hung up on iconv  
issue -- see previous post).

Thanks,
Fred