No idea why the sudden change, but I've got a Level 9 Bugbear Rogue who has had a Large Frost Dagger +2 eqipped for months, and now all of a sudden it won't equip. Its not red, so its not even a Proficiency issue.
Anyone else care to try a Level 9 Bugbear Rogue with a Large Frost Dagger +2 & see what happens?