Whenever you click the top of the window in scratch (almost everywhere here)and you don't click a button, your mouse stays there for a long time and you can't move it.
I'm taking a break from Scratch until 2.0 comes out. Any messages sent between then and now probably won't be read - sorry. (Oct. 20, 2011)
There may be an error on your version of Scratch. Such as missing codes. If that is the case, try installing the latest version of Scratch from the Scratch website. You can access the download page via the Scratch home page.