Compressor doesn't understand I have 2 drives

I have an external blu-ray drive hooked up to my iMac, and Compressor has problems recognizing which drive I want to use, the blu-ray or the internal DVD drive. Today when I tried to burn a regular DVD from Compressor and it asked me to insert a DVD it just ignored it. I tried the blu-ray drive and it ejected the DVD. I tried disconnecting the blu-ray drive and then inserting the DVD, and again Compressor ignored it. Similarly when I try to burn blu-rays the blu-ray disc will just sit there in the drive with my progress bar stuck at about 58%. Sometimes it will eventually recognize that the disc is there and start burning, but other times not and I have to start over.
Isn't there some way to tell Compressor which drive I want to use? I don't see anything in preferences.
My workaround today is to use Toast to burn the already-created ac3 and m2v files, but I worry that it will not do as good a job with the encoding. Checking now to see if the disc looks ok..
Well it looks ok I guess but I shouldn't have to do this!