Strange but I found the same thing happening. was working, charging etc. when i plugging into my PC it was charging and recognized but after trying the "Switch Device" thing it no longer recognized or charged on any computer or the wall charger. I was ready to throw it in the trash when I saw that I had discarded the USB cable that came with the 8330(I figured I have too many of these BB usb cables), I gave that cable a shot and all the sudden working and charging perfectly.
keep you posted on further developments but for now its a quick fix that's working for me.