How was it packaged? That will make the biggest difference.
Also, most home freezers are not set cold enough to hold foods past 6 months without starting to become freezer burned or tasting off, unless stored in special shrink bags for freezing (Cryovac).

Is it clear or not is the Use By date is refering to the frozen product? I have never seen ham offered for sale frozen. Usually it is fresh, and the use by date would refer to the fresh product, so in that case, May 2010 would be safe if frozen. How long have you had it frozen? Is it frozen at zero? What kind of ham is it?

University of Illinois Extension says best quality for frozen ham it by Use By date. http://wellnessways.aces.illinois.edu/Commodity/ho_HamFS.pdf