I've had the book from the library before, but I can't remember if it's Magic Loop or 2 circ method.
I do 2 socks at a time on 2 circs all the time. If I have to unravel more then a row or 2 on only one of the socks, I just move the good sock to a separate needle and work on just the one sock until I get it back on course and then join them up again on the 2 circs.
It would help to know which sock you're making. And even which method it is and where exactly in the pattern you're having trouble. Could be someone w/out the book can help, too, w/some more information.