Jack Simth
First Post
According to the Rules Compendium, the Rules Compendium is the final word.According to the Rules Compendium (which is, I believe, the final word): "The creature retains the special qualities of its natural form." This was also the rule according to the 3.5 Monster Manual errata. IIRC there was some mucking up of the polymorph rules in the PHB2, but as I said, the Rules Compendium seems pretty clear that you do not lose immunities / resistances / regeneration / fast healing.
According to the header on every single piece of errata for the DMG, PHB, and MMI, the DMG, PHB, and MMI are the final word.