roachboy --
I'm willing to accept that there might not be a reason for everything. I don't personally believe that, but I don't have any generally valid reasons for my own beliefs either. It's just a premise for me. But if there's not a reason for everything, the op's question seems like a very, very good candidate for a question there's just no answer to.
To the extent that your response is saying that the principle of sufficient reason is a principle assumed by theists, I think you're mistaken. Of course, the origin of these sorts of arguments is Aristotle, and he wasn't exactly the sort of theist you tend to run into these days. It's probably a difficult historical question (regarding how influenced he was my Plato's own beliefs regarding 'god'), but it seems very unlikely he was culturally influenced into a belief in a creator God, and somewhat more likely that he viewed this belief as a necessary result of his philosophy. (Speaking of irrational fears, how about Aristotle's irrational fear of infinite serieses?
)
And what's the plural of 'series', anyway? ...