Sometimes the "Enchant" button disappears for padded armor (see attached screenshot)

 

 

I also noticed at the same time that accuracy rating shown in the character sheet for one of characters was wrong. After I quit the game and reloaded the next day both the enchant button and the acc. rating were displayed correctly. My guess is that after a long playing session there is some memory corruption.

I've seen it happen as well. Usually it clears up after just a reload though, you don't need to restart the game for it.