Sometimes the script recorder records a transaction but upon playback the script errors because certain things in the page has changed. The most common reason for these issues is that during record, the transaction recorded relied on cookies that were already stored on the local machine. An example of this is a cookie that stores login information. Once logged into a certain site, the user will remain logged for an extended period of time. While recording, the browser will display a page that already has the user logged in while during playback, the user is logged out and will require the script to log the user in.
During playback, the script will always create a temporary internet file space and a temporary cookie space. It will play back as if it is Internet Explorer running for the first time. For this reason, it is recommended that the cookies are cleared prior to recording a transaction that may rely on those cookies.
To clear your cache, go to the 'Tools' menu in the recorder and click 'Clear Cache'