hi tom, at least good to hear you have it working again ...
in apple keyboards, iMacs and apple displays you can find a wide range of USB hubs - eg. many devices don't work at all if they're plugged into the keyboard ...
i know it doesn't help, but here is another strange story: for certain tasks i have a G4 mirrordoor standing beneath my desk with a generic (powered) hub which is needed because of only 3 USB ports ... while it wortked with 3 or 4 keys under 10.4.8 the same does not work with only 2 keys in 10.4.11 ... and i have absolutely no idea what might cause this behaviour because phisically nothing has changed.
another annoying issue here with the apple display firewire hub - it is impossible to get any firewire disk (even a LaCie) mounted if connected to the display, but i'm considering it hopeless to get that solved by anyone ...
third story (PC related in this case): we have a USB M-Audio keyboard which disconnects every time when a certain neon light is switched on or off (which is connected to a very different circuit btw) ... so who's to blame: the electricity company, the vendor of the lamp or the switch, M-Audio, the cable company? ... i don't know ... i simply don't switch it on or off when working ...
christian
and remember: only a CRAY can run an endless loop in just three seconds.