I don't recall anyone else reporting this issue.
At least in D2:ED, entering Maxos temple finished the Paper Trail quest, and a conversation automatically started with Zandalor. Did everything appear normal when you entered, apart from not being able to use the standard melee attack?
Can you swing your sword(s) again if you leave the temple?
Did you try switching to a different combat style? (unarmed, duel wielding, one or two handed, sword and shield)
You could head to the fjords, by the path to the far southwest in Broken Valley (the opponents along the mountain trail are level 18, but the initial area is safe). When you return, maybe getting the game to reload the Broken Valley and then Maxos Temple areas might possibly get your melee attack working.
