Other USB devices work fine, e.g. Flash drives and my Iomega Zip250.
Then your Apple USB drivers are probably NOT the issue.
...I have OS 9.2.1 (1.5.5) versions of the latter four...
If you are running 9.2.1, that is exactly what you should have.
I also have two extras that you didn't list above:
USB HID Driver 1.2.5f6
USB Sentinel 2.0
Select the extension and choose Get Info from the file menu. Often, the copyright holder and the OS version supported will be displayed. Are these Apple extensions? They may have been added by one of your devices to provide support for OS 8.
I don't see why USB Authoring Support should be needed, or the printer extensions, but i guess i can try the above combination and see if it works.
Feel free to leave them out if you wish. I listed the complete set of extensions installed because some users cannot re-install OS9 but can chase down the individual extensions (much more work in most cases) and need to know what versions to be looking for.