affecting me in Vvardenfell and others, according to zone chat. Some were able to queue recently for a random normal, but not for a vet dungeon. I was just trying to queue for a random battleground. I'll try again later. Just logged on after dinner so don't know exactly when this issue started. I saw it about 10:25pm EDT (Monday May 6). Guildmates indicate it may have started a bit earlier, about 10:15pm.
Update: as of 10:40pm EDT, I can queue again (now in the Brass Fortress), but the common "someone declined" issue is acting up fiercely... I eventually declined the invite myself, after accepting at least 40 times and it still not successfully forming a group. Time to go do some dailies.
Update: as of and since May 7, I have not seen the "Unable to queue at this time" issue again. The "Someone declined the invitation, you have been placed at the front of the queue" (or something like that) still happens quite often.