I have found the issue with mine. I had bought a 2nd 250 chip to build a second mod, this works perfectly with my PC even without a battery fitted (screen won't switch on without the battery connected).
When installing the battery I shorted out a couple of the charge wires I was not aware of this until I plugged in the battery and, pop. The unit charges fine and I can use it as normal I just can't do any updates on my computer.