I have installed:

XFree86-100dpi-fonts-3.3.6-20
XFree86-3.3.6-20
XFree86-75dpi-fonts-3.3.6-20
XFree86-Mach64-3.3.6-20
XFree86-Xvfb-3.3.6-20
XFree86-devel-3.3.6-20
XFree86-doc-3.3.6-20
XFree86-libs-3.3.6-20
XFree86-xfs-3.3.6-20
xboing-2.4-10

My xinit output is:
XFree86 Version 3.3.6 / X Window System
(protocol Version 11, revision 0, vendor release 6300)
Release Date: January 8 2000
	If the server is older than 6-12 months, or if your card is newer
	than the above date, look for a newer version before reporting
	problems.  (see http://www.XFree86.Org/FAQ)
Operating System: Linux 2.2.5-22smp i686 [ELF]
Configured drivers:
  Mach64: accelerated server for ATI Mach64 graphics adaptors (Patchlevel
1)
(using VT number 7)

XF86Config: /usr/X11R6/lib/X11/XF86Config
(**) stands for supplied, (--) stands for probed/default values
(**) XKB: rules: "xfree86"
(**) XKB: model: "pc104"
(**) XKB: layout: "en_US"
(**) Mouse: type: PS/2, device: /dev/mouse, buttons: 3
(**) Mach64: Graphics device ID: "3D Rage Pro AGP 1X/2X"
(**) Mach64: Monitor ID: "CTX 1785GM"
(**) FontPath set to "unix/:-1"
(--) Mach64: PCI: Mach64 RagePro rev 92, Aperture @ 0xfd000000, Registers @
0xfe6ff000, Block I/O @ 0xd800
(--) Mach64: PCI (92) and CONFIG_CHIP_ID (124) don't agree on ChipRev,
	using PCI value
(--) Mach64: Card type: AGP
(--) Mach64: Memory type: SDRAM (4)
(--) Mach64: Clock type: Internal
(--) Mach64: Maximum allowed dot-clock: 230.000 MHz
(**) Mach64: Mode "1280x1024": mode clock =  80.000
(--) Mach64: Virtual resolution: 1280x1024
(**) Mach64: Video RAM: 8192k
(**) Mach64: Using software cursor
(--) Mach64: Using 16 MB aperture @ 0xfd000000
(--) Mach64: Using 4 KB register aperture @ 0xfe6ff000
(--) Mach64: Ramdac is Internal
(--) Mach64: Ramdac speed: 230 MHz
(**) Mach64: Color weight: 565
(--) Mach64: Pixmap cache: 2 256x256 slots, 8 128x128 slots, 32 64x64 slots
(--) Mach64: Font cache: 16 fonts

When I run "xboing" and move the mouse over the xboing window, the cursor
is supposed to disappear; instead, I get a weird streak, about fifty pixels
wide, from where the cursor is down to the bottom of the screen.

This goes away when I enable the "sw_cursor" option in XF86Config.