I first noticed this two days ago, but it could have been in existence for a while. I tried to wear an outfit I haven't worn in some time by right clicking the folder and choosing "Wear all". All of the object prims in the folder attached EXCEPT three object. These three refuse to attach, and no message is given about an attachment pending. I am unable to rez them in-world and I am unable to attach them to a different location point. I tried clearing cache, I tried attempting the same procedure in the Release Candidate, to no avail.
The designer sent me new versions (they were no copy, no mod) and those attach just fine.
Last night, I had the same thing happen, again with an object I've had in my inventory for months. This time it's copiable so I made a copy - the copy also refuses to attach or rez in-world. That one is a freebie I picked up somewhere and I'll have to replace it myself.
In sum, something is breaking random objects permanently in the inventory.