If your Mac is not recognizing the devices plugged in to one of USB ports, Dont be worried, Just read this passage.
If nothing happens, turn off your Mac, unplug the power cable, disconnect all peripherals, and let it sit for five minutes. Plug it back in, reconnect the keyboard and mouse, turn it back on, and try the USB ports again.
Check the Support Downloads page for firmware updates for your Mac.
If they’re still unresponsive, you will need to reset the PRAM (parameter RAM) and NVRAM (nonvolatile RAM), which stores some system and device settings that your Mac accesses on startup. Shut your Mac down. Then position your fingers above the Command, Option, P, and R keys on your keyboard. Turn the Mac on, then immediately press and hold those four keys before you see the gray screen. Keep them pressed until the Mac restarts again and you hear the startup chime for the second time. Then let ’em go. When your Mac is finished starting up, check those pesky USB ports.
If they’re still not behaving, there’s one more thing you can try before making a Genius Bar appointment: resetting the SMC, or system management controller. Directions for resetting the SMC on your MacBook Pro are found at support.apple.com/kb/HT1411. Instructions for all other Macs are linked from support.apple.com/kb/HT1894.