Late 2011 MacBook Pro; one USB port not recognising anything

Hi,

I've had my MacBook Pro since January 2012, so I believe it is the late 2011 13" model. I'm currently running OSX 10.9 although the problem I've been having has been going on around 3 or 4 months, I think I had OSX 10.7 installed when the problem started.

One of the USB ports on my Mac (the one on the left when looking at them face on) is not recognising my external hard drives, or recognising/charging my iPhone when plugged into the USB. The other USB slot works fine and recognises external hard drives, however when I insert the hard drive into the faulty USB input, although the hard drive lights up and starts whirring as if it is ready to start functioning, it does not appear under the 'Devices' tab of the Finder screen, but does appear and function when using the other port.

Similarly, when I plug my iPhone 5 into the faulty port it is not recognised/does not start charging, however if I leave it running and come back later I often have at least a level of increased battery life which suggests that it does intermittently charge from time to time, and again it functions normally when using the fully functional port.

I've tried the NVRAM reset as I have read in another post but to no avail. Is this likely to be a mechanical fault over a software problem, and if so what could be wrong with it?

Thanks for the help in advance.