If you have had any weird, solid, lock-ups with your PowerBook when using OS9 & OE5/IE4.5 I would suggest you try the following:
Boot with your old 8.5 or 8.6 CD, run DriveSetup and downgrade your disk drivers. I have been running without any problems for the last 3 days. The real stress test will be when I get back to work on Monday, but it looks good so far.
freedom