"Your site has been assigned special crawl rate settings. You will not be able to change the crawl rate."
Google doesn't necessarily explain these things. I have the same message on a long-established site. Not a problem. They crawl it just fine.
Just means either they will crawl it more often or less often. Like I know big sites like this and myspace and such would have a higher crawl because its updated a lot more. Just dont worry about it to much.
I thing trough webmast4ere tool we can do it, but Google not considering it .. if the content is updating regularly then Google itself increase the crawl rate