as above. This seems to happen to me quite often and I've spoke to a few other players who are getting this too. When my melee only creatures are entangled, they can't attack, even creatures or figures that are adjacent to them, but often my opponents entangled creatures can attack anything that is adjacent to them. I've looked carefully at the creature cards and payed attention to enchantments in play, but I still find no reason why opponents creatures attack and mine don't. I am using the 3d-client, and the other players I've spoken to about this are too. Is there some kind of incompatibility between the 2d and 3d clients?

either you attacked them (and they can attack back), or they're on a desert (and entangle has no effect on desert).

There are cases where they can still melee: http://thefarwilds.com/wiki/index.php/Entangle