Bug as of 4/6/2015 (after installing the recently released patch). I downloaded the game from GOG and just downloaded the patch off of GOG and installed it.
After the patch, when I click on my currently equipped weapon to toggle between weapon sets, I can toggle to weapon set III even though weapon set III is locked on the inventory screen. I should not be able to toggle to weapon set III.
Since weapons set III is locked on the inventroy screen, I cannot put any weapons in weapon set III, so when the glitch occurs and allows me to toggle to weapon set III, it just shows a fist. This bug was not present prior to the most recent patch. I was playing a human Chanter when I noticed the bug (in case that matters at all).
I cannot toggle to weapon set IV (which is correct, since weapons set IV is locked).