Selenium. I can't back this up with anything but my own experience. When I first started supping, I had insomnia as well. And I'm normally a very good sleeper. Starting with selenium normalized my sleep(200mcg). I was using brazil nuts, but too much variation in Se content...
It was either the selenium or exhaustion that fixed it:)
You know what I remember though? The insomnia didn't really bother me. I felt SO good otherwise. I kind of liked it, in a strange way.
In this link, Lynn122's post is a lift of an old post of mine(that I can't find)(BTW, wrote that post when suffering insomnia). The link that I reply with is the source for the selenium/sleep info: