As you are unlikely to have another Nokia device using BL-5C to check, it would seem time to return this device if still covered by warranty.
Happy to have helped forum with a Support Ratio = 42.5
My daughter's 360 is doing the same thing. Was there any solution to this issue? I'm thinking there's a problem with the micro USB port.
This may suggest a hardware problem and I do advise sending the device to a Nokia Care Centre.
To locate a Care Point near you, please use the locator which can be navigated from this page http://www.nokia.com/global/support