Totally discharging the battery is the way to go. But what you can also do to use your phone in the meantime is this. Plug your charger into the phone withOUT your battery in. It will tell you "Unable to Charge." When it says this, put the battery in. It might tell you "Invalid Battery" a couple more times, but it did eventually say "Charging Battery" for me. After that, simply turn the phone on and it will return to normal. This is when you drain the battery completely. Once I did that, I did not get the invalid battery error again.