It's hard to tell what's going on. First, why doesn't your 1080p television handle 1080? Is it connected to your AVR with HDMI?
I don't think your problem is with the DVD player; it doesn't know or care what your monitor is, it's just sending a signal. I think it's your TV. You should be able to set the format. I don't have a Toshiba but I do have both a Sharp and a Panasonic and, although the terminology is different, they handle things the same. Bring up your menu for the TV. You should see something like "aspect ratio". My Panasonic defaults to whatever is sent to it or you can Zoom. The Sharp has a "bit by bit" setting which just puts on the screen whatever signal it gets or it has a Smart Zoom and a Zoom (the Smart Zoom is the same as Zoom but it respects the borders of the screen better so the picture doesn't go off the screen).
Play around with those settings and your problem should get resolved. If not, post back with the model number of the Toshiba and some additional info on how things are hooked up (DVD to AVR, AVR to TV).
Joe
If you can't have fun doing it, it's probably not worth doing.