I've tried a few micro USB leads with my new Desire and, even though they're all good, only some allow the PC to connect to the phone. Not sure if this is the same issue or not. Anyway, when I use a lead it doesn't like the charge light comes on on the phone, but the device shows as unknown in Windows. Not sure if charging is slow or not. When it doesn't like a lead, that lead will never work with the phone, but when it does like it, it will always work.