While BeOS 5 supports mouse wheels on virtually all PS/2 and USB mice, two exceptions appear to be Logitech USB mice and MS Intellieye USB mice.
If you’re using a Microsoft Intellieye mouse on the USB interface, you’ll notice that the scroll wheel does not work in BEOS 5. The fix is simple — shut down and hook up the USB to PS/2 adapter that comes with the mouse. Plug it into the PS/2 port, reboot and the wheel will work perfectly.