Unreliable detection of USB devices

[John O'Brien]

I have a 15" SuperDrive PowerBook and am finding USB devices not 
exactly plug-and-play. Some devices always work, some only occasionally 
work, and others only work in one of the two ports. They'll show up in 
the System Profiler but the OS itself won't recognise them. Devices 
include USB-serial mouse adapter, USB-IrDA adapter and USB Flash memory 
bar.

These are devices for which the drivers are built-in to OS X, by the 
way. Does this sound like a hardware, software or firmware problem?