What happened to my battle pets?

A few days ago, I opened my pet journal, reordered it to sort by level instead of by name (as I always do), and noticed that some of my battle pets seemed to be missing. Scrolling down the list, I found the missing pets with the pets that cannot battle. They were greyed out and, when I selected them, unsummonable.

Have any of you been experiencing this with your battle pets recently, too? Any ideas what’s going on here?
I thought that maybe I had too many pets favorited, as I’d recently promoted several more pets to Favorite status, but de-favoriting some of those pets didn’t restore the greyed out ones to activity.
I’ve submitted a bug report about it, because I am really puzzled about what could have triggered it and I have no idea how to fix it.

Update (Friday night): Looking at my pet journal again just now, I discovered that all of my disabled pets are are not tradeable, Unique, and from the Blizzard Store (except for the Dread Raven Hatchling, which is from the Warlords deluxe edition)… but I have pets that fit all of those categories that are still active, too.

Update 2 (Saturday night): Well, whatever the bug was, I guess it got fixed. Apparently it affected my mount list, too, because the first character I logged in with today had mail from Mei Francis containing all my mounts from the Blizzard Store, plus the Dread Raven mount. (I had been puzzled by one of my mount macros failing last week, but it only happened once, so I hadn’t investigated the problem further.) When I then checked my pet list, my disabled pets were all restored to activity.