My F2Ps and vets can still queue.
OP, you might be experiencing what I experienced on my vet warrior some weeks back. When I logged onto my toon, I noticed my XP wasn't locked (even though I locked it). I went to lock my XP and Slahtz <Experience Eliminator> took my gold, and it essentially locked my XP but then it gave me that error. It said I couldn't queue BGs.
Basically, I talked to him again and told him that I wanted to gain XP again. He proceed to keep taking my gold and doing nothing. I still wasn't able to queue until I re-logged. If I talked to him again, it would bug out again until I re-logged.
I assume it's related to the inability to queue 19s on an un-subbed account.