The behavior of skimmers have always been a complete mystery to me. Who knows what events take place within a tank to trigger a runaway skimmer. So many factors to fathom. Too much for my little mind. Shrimp or any other spawning event (sudden protein releases) can certainly be a factor.
My skimmer did that from time to time early on as well. As your tank ages this seems to slow down and eventualy stop. Has for me. Im like Jerry, I have no idea why but something you have to keep an eye on for a while. Id say around the 5 month mark was when my system lvled out and is predictable as far as running the skimmer wet or dry. I can set it to run black water or gray with out fear of overflow. Give it time.
I think everyone who has ever owned a skimmer has dealt with this problem. Things like the natural oils on your hands can make a skimmer go nuts. Like Nate said try to skim a little dryer and remember if it Ain't broke done't fix it!!!!!!