I assume you tried the rear USB ports and they work OK.
That would mean that the front ports are not properly grounded.
It would likely be difficult to fix.
Someone would have to speed a great deal of time finding the source of the problem.
I suggest you buy a USB extension cable and plug it into one of the rear ports and leave the open end near the front of the computer.
That way, it would be handy when you wanted to plug/unplug the PDA/Camera.
Here is a such a cable:
Every single time I unplug anything plugged into any of the front ports, the whole pc shuts down! Can anyone tell me why and how to fix it? Thanks!
System: Acer Aspire 380, Windows Vista