How do you connect these USB devices to the computer?
Through a hub? Is it a powered hub or a passive hub?
How is the hub connected to the computer, via a =built-in= port or on a PCI card?
Maybe you are connecting the usb devices in a =daisy chain=?
If the printer is connected directly to the computer and the other devices are connected to the hub, does the situation change - impove or get worse or stay the same?
I think there is a limit to the number of devices that can be connected directly to the computer, using a built in port; but using a powered hub the total number is 128.
Have you searched on Google for the topic of USB? That's a good place to at at least find out what USB is supposed to do. In my configuration for example, when the printer is connected to the system a shutdown command is treated like a restart command. Remove the printer and the computer will shut down.
If all else fails, you might want to add a USB PCI card to your computer.