Short Description: Magic Fang (druid spell) will suppress weapon special effects (such as Flaming, Frost, etc.) when swapping weapons.
Long Description: It seems that Magic Fang is "tied" to the weapon which is equipped at the moment you cast it. That's fine. However, if you switch weapons a very odd effect happens. The newly equipped weapon (which does not have magic fang on it) will not deal any special damage (holy, flaming, pure good, even Ghost Touch are suppressed).
Steps to reproduce bug:
1. Enter animal form (in my case, wolf)
2. Equip a weapon which has a special effect, such as a +1 Flaming Scimitar.
3. Cast Magic Fang.
4. Attack a Training dummy or real enemy, notice that you properly deal fire damage on each attack.
5a. Remaining in Wolf form, swap to a +1 Shock Scimitar.
6a. Attack dummy/monster again. Notice the bug: you are not dealing any electric damage.
5b. Remaining in Wolf form, swap to a +1 Scimitar of Pure Good
6b. Attack dummy/monster again. Notice the bug: you are not dealing any good damage.
5c. Remaining in Wolf form, swap to a +1 Ghost Touch Scimitar
6c. Attack an incorporeal monster. Notice the bug: you sometimes get "Incorporeal" messages as you miss, despite ghost touch.