Hi, Thank you so much!
I studiously went through and deleted everything pertaining to Roxio Toast (absolutely AMAZing where they hides ^#!&) reinstalled (again). I started getting error messages about .kext files, so I went to:
and dl'd Kext Utility.app and ran it. Rebooted and then got a message that there was no burner--check the cables, etc.--which is funny as I have an iMac. Ran the Kext Utility again for good measure (no idea if that had anything to do w/ it or not), rebooted, and Viola!
In answer to your question, I am running 11.0 and am quite frankly reticent to poke the bear since it is running perfectly now (knock wood). Also, I know it wasn't the file type as I had just burned the exact same .avi to disk earlier in the day and I used that same one to test it. The only things I can think of were I ran DriveGenius to get rid of PPC binaries and unused localizations, and I also disabled the APE for another application. This was 10 hours of my life I won't get back, but, again, thanks for your help!