Dick,
Welcome to the world of flaky USB!! First, make sure a) your hub is either USB 2.0 (faster) or USB 1.1 and b) check each USB device to see if it is USB 2.0 or USB 1.1 type. Now comes the problem. First, if your Mac is newer it should have all USB 2.0 ports. If you connect a USB 1.1 device to a USB 2.0 port, the port will work but all other USB devices connected to that port will slow down to USB 1.1 speed.
One possibility is that you may be connecting 2.0 and 1.1 devices to either a USB 2.0 hub or port. This shouldn't be a problem but to be on the safe side, since my three USB buses are USB 2.O, I have two hubs: a) an USB 1.1 for keyboard, mouse, and any 1.1 flash drives and b) an USB 2.0 for all my 2.0 devices. Therefore, I sacrifice only one USB 2 bus to slower USB 1.1 devices.
for a device
Frankly, if you understand what I just wrote, I am awarding you a PhD in EE!! Even I, sans an EE degree, am confused.
On the other hand, as Tevye the dairy man would say, it could just be the USB (Universal Standard Bus)( protocol
may be a bad design and doesn't work with Apple's protocol.
Now that I succinctly and clearly explained this matter to you, you should raring to go smoothly down the path towards computer nirvana!!
MamaMoose