The basic argument of Sola Scriptura is that all Christian teachings and traditions are to be founded in and subservient to the Bible, and in nothing else. Obviously this does not mean that there are to be no Christian traditions, but rather that they are to be biblically-based.
How does this tally with the history of how the Biblical canon was formed and the criteria (tradition) according to which the canon was chosen and closed? How can this formation have been founded on the Bible, if there was no Biblical canon to start with (especially with regards to the Gospels and the NT in general)?