I think I found a pattern, that the "mouse freeze" happens more often when the alt key is used to select the startup the volume instead of letting it auto select on boot...
In reference to DieHard’s comments regarding info on mouse
freezes with dual-boot Mac minis...
and the alt/option-key boot… I wonder if kgllewellyn’s eMac approach (or a suitably
adjusted variant)
with a Mac Mini - might be relevant / useful?
http://macos9lives.com/smforum/index.php/topic,4361.msg35831.html#msg35831#!/bin/sh
echo Enabling OS 9 booting...
echo "You may have to enter your password"
# Use nvram command to setup nvramrc with script to make open firmware changes
sudo nvram nvramrc='" /" select-dev
" PowerMac4,4" encode-string " model" property
" PowerMac4,4" encode-string " MacRISC" encode-string encode+ " MacRISC2" encode-string encode+ " MacRISC3" encode-string encode+ " Power Macintosh" encode-string encode+ " compatible" property
unselect
'
# Enable use of nvramrc on boot. Change to "false" if you want to disable again. Or just clear/reset nvram.
sudo nvram "use-nvramrc?"=true
echo done.