Only thing that makes no sense - usually when something like this happens, a connection to a solder tab has come loose, but you're seeing half voltage in each cell which implies that's not happening. If both individual cells are still intact, then something is going on in the media which is prob not good, raising voltage and lowering amp production. I haven't heard of a lipo dieing with these symptoms. This might be unsafe....

That said, have you tried to discharging to see if voltage will come down so your charger will accept it? Watch for any signs that cells are starting to puff.