Most of the times the ports are just fine and the issue is either driver or cable/HDD enclosure related one. Generally, external HDD tend to be less reliable than internals, so it is always a good idea to keep your data stored on at least two place.
Also, the USB ports on the back are directly attached to the MOBO. So, when you think that a certain USB port is going bad, you can just attach the device to these ports.
Apart from all this, I guess you can go to the MOBO's website and update your USB drivers. This could sort some of the USB related issues out.
Regarding the monitor sound, I guess you could update its drivers as well. If this doesn't solve the problem, you can just contact its manufacturer(e-mail, phone, etc.)
Cheers,
D_Know_WD