The service guy is probably right, but wants to charge a lot just to take off the cover, inspect and solder a few joints.
I have found that the solder joints on the USB metal housing are insufficient.
This causes the USB metal housing to flex when connectors are inserted.
With continued use, the solder joints of the 4 electrical wiring pins crack, which causes the port to become intermittent.
Devices that use a lot of current, such as external DVD drives seem to have the problem worse than a low power mouse. But eventually the port stops working.
Search on Youtube for one of my videos, that is showing a BDROM replacement.
After the dis-assembly and BDROM replacement, at 9m:20s I also show the USB ports with this problem, and how I fix it.
Search for " Sony Vaio VGN-AW BlueRay DVD BDROM Replacement BC-5500S"
To fix it, you will have to take the back off of the laptop, a bunch of screws.
Draw the outline of your laptop on a piece of paper, and tape the screws on the paper in the position thatthey were removed. Makes it easier to put it back together because of the different sizes.
Remove the USB port which is usually just one screw and a few connectors.
Look at it with a microscope, and you will see the cracked solder joints.
Get someone that is good with soldering, and have them re-solder the joints. Use some additional lead solder and do use "rosin" flux. (SN63PB37 RMA)
Should not cost you anything.
Austin_semiconductor
Allen TX