FIRST, CALL AN ELECTRICIAN, I agree with the other posts.
I've known several people that has a floating neutral outside the house, in both cases fairly extensive damage was done before it was corrected. In both cases it was a power company issue, i.e. beyond the meter box.
While you're waiting for the electrician (you did call him, right?), check the voltage on each phase of your power. They should be very closely matched, certainly within a couple of volts. If a high current device like a hair dryer being turned on causes that phase to drop in voltage and the other phase to rise in voltage, you likely do have a neutral issue.
