Hi,
it sounds like DownloadStudio is getting the wrong cookie for Rapidshare, there may be an older invalid cookie in Firefox or Internet Explorer that is being used, you will need to clear out the cookies in Internet Explorer and find any Rapidshare cookies in Firefox and delete them. Once you have cleared the cookies from these browsers, DownloadStudio should be able to find the valid cookie from Chrome when you create new Rapidshare download jobs.