Exact same results here with an Intel iMac; 7.1.2 -- no burning to DVD-RW; drop back to 7.1, -- no problems.
I realize it's easy to point the finger at problems or quick with Apple burners, but the fact remains that Toast 7.1 works fine with those "problems" and 7.1.2 doesn't (and, according to other posts, version 8 won't either).
As much as I'd like to upgrade to version 8, I can't justify it if it means I have to buy a new DVD burner to use it. Perhaps Roxio should investigate a little further and find out exactly what changes to the Toast code removed compatibility with burning rewriteables, and either change it back or add the option of turning off whatever feature required the change to allow people to still burn rewritables?
-- Walt Sterdan