Dan, check the archives
Your generator is probably OK, its just how the neutral and ground are produced internally in the generator.If I remember correctly, the generator produces a 120V output with 60V on the neutral and hot with respect to ground.At your house, your 120 is produced by a 120/240 volt source with the neutral and ground at the center tap. So, you get 120V on each leg of the hot. So there is no potential between neutral and ground. The generator may have 60 volts on the neutral with respect to ground.I could sware I remember the generator producing a 60/120 volt source, and the ground was connected at the center tap.Check the archives - I could be wrong.