All mobs invulnerable to melee.
 

Title sums it up fairly simply... all mobs are invuln to melee. Had this problem once before and a server reset fixed it, but it didn't this time around. Could I have accidentally modded them all in my DB or something?

Check the required level on the weapons you are using. If you don't meet the requirements for an item, they won't work and you will get the invuln message. Maybe you are using level 75 weapons and aren't level 75.

Accidentally edited Rusty Dagger while modding the drop tables for a few mobs ( made it 75 req ). Thanks Trevius.