error multisim 11.0

Hi I have just got a copy of multisim and when simulating a very simple 1:1 transformer with 240VAC 50HZ to a bridge rectifier, I am getting 90 something volts! The ac from the traf is reading 240 but after the bridge it all goes pete tong. What can I do? I assure you that there are no stupid noob mistakes. Thanks for reading