Keep running your OSX 10.3.9. You may well be safer there.
I have a Maxtor FW storage device that won't mount. I can tell you with absolute certainty this: OSX 10.4.4/10.4.5 updates have caused multiple problems internally with software, as well as with 3rd party external devices. I know, because none of the trouble began until then & that was the only thing I did different—update to OSX 10.4.4, then 10.4.5. Unfortunately, I didn't recognize the problem with 10.4.4. Some CD/DVDs just wouldn't mount — others would. Then 10.4.5 — it was curtains!
I haven't seen any workable posts yet for me, but, I am going to try your OS9 startup suggestion. I've got nothing to lose at this point. If I can get my FW device back I will be a very happy camper. This is the first time ever that I have had problems with Mac updates, and multiple problems to boot.
Good luck to everyone. Let Apple know so they know it's a big problem by the response of users. So far they haven't created any fixes, just security updates. Are they really secure? LOL Secure for who? LOL