"Voltage source is shorted" simulation error
This is because using nodal analysis and the superpostion princicple (for independent sources), you would normally analyze the circuit once source at the time, with other voltage sources shorted, and then add the results. Obviously, shorting one source also shorts the other, hence the error.
The error makes sense - the circuit cannot be analyzed as currents would be infinite. So no ideal analysis will be able to solve the circuit.