I'll second that. You need to get a true test by disconnecting all loads (shut off all mains) and measure leg-to-leg. If you don't get 240 there, then one of the legs has failed. At that point, your problem would likely become the power company's problem.
What kind of 240 volt loads do you have in this situation? Those will dramatically affect your testing with the power on. If you have an electric stove or dryer, turn them on to maximum and see if your voltage readings change. I'll bet that they will, indicating the failure of a hot leg. You'll still pick up 120V to neutral on one leg, but some wacky voltage on the other leg to neutral.
Oddly, this probably won't do nearly the amount of harm to connected equipment that a failed neutral would. At least the voltage is low and not high as with a failed neutral.
Sounds like it's time to call the power company.
