We had this EXACT problem here a few years ago, 60V on one phase of a 120Y/208 secondary, and wierd things afoot because of it (some equipment on an outlet working fine, others not, computers that seemed powered up until you tried to turn them on, etc). In our case, it turned out to be a lost phase in the utility line. I unfortunately can't recall the details of the utility line problem, but it should be easy enough to determine if the problem is on the poco side- are the neighbors complaining, too?
