After updating Hummingbird to the latest version there seems to be a problem after re-cashing the files in humming bird ("RE-CHECK FILES" Button on the minify page).
As i made some change to one of the CSS files i had to reload the files so the css was updated in the combined/minified version. I did this by clicking the button in the minify page and it came up with a notice that the files had been recached.
At first the files where not getting combined nor minified. after about 10 minutes (during the time of opening this ticket) the files suddenly where minified and combined. before updating changes where published instantly.