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There is a known problem with many third party USB devices and Energy Saver (also known as sleep), not cooperating. In many cases this is because when it wakes from sleep, the USB bus is in a lower powered mode than prior to sleep's initiation. To fix the problem, restart the computer, or at least wait for the clock to begin working in the menubar before reconnecting a third party USB device you find is having problems. You may find the system temporarily freezes after waking from sleep with third party USB devices that are affected being connected. If the freeze is more than temporary, and force quitting with command-option-escape (command is the Apple logo key on the Apple keyboard) key sequence doesn't work, you may be forced to rebuild your directory. Use Desktop & Screen Saver's Screen Saver, Screen Saver or Screen Effects in Apple menu -> System Preferences (depending on your version of Mac OS X it is called one or the other) instead of Energy Saver if you want to save your computer's screen and have those devices constantly connected without issue. Connecting those devices to a wall powered USB hub may also work better than connecting them directly to the computer.
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