I was testing to make sure my Ranger and my Spellblade could both cast Jump. Had to buy them a Focus, but that was okay (I knew I'd have to do this from previous playthroughs. There's still an issue for first-time players who likely wouldn't discover their inability to cast until they were deep into a dungeon.)
When I hit "Cast Spell" with my dual-wielding Ranger, Jump was disabled with the note "No free hand to perform somatic spell components". Fair enough. I then clicked Abort and switched to bow. Clicked on Cast Spell and since you can hold a bow 1-handed while you cast with the other, it shows Jump as being a cast-able spell.
Then I thought "I wonder...". So while the spell selection menu was up, I clicked on his dual Scimitars. The attack action updated. The character model updated. But the spell selection menu was still displayed and Jump was still enabled. Technically, Jump should have become disabled.
Granted, this is pretty nit-picky and an edge-case -- it's not too likely that anyone is going to switch weapons in the middle of casting a spell. However, the bug also exists in reverse: if both hands are full and you go to cast and discover you can't, switching weapons to something that should allow casting won't enable the spell either.
It's far from a fatal bug and clicking "Abort" and then "Cast Spell" picks up the right rule so there is a workaround. Everything else in the game is just so perfect though... little things like this stand out. :) Keep up the great work!