If you are working in SharePoint 2010 and discover that users in the Visitors group or All Authenticated Users are unable to open pages that contain a Report Services web part with an Access Denied error you might think the issue is related to permissions. Then again, it may just be something quirky about the platform that prevents groups with Read permission from seeing reports that were published as a minor version.

The solution: make sure the reports are published as a Major version. You can use “draft check” button on page tab of the ribbon bar to Publish a Major Version, or change the Report Library versioning settings to publish only major versions and re-save the reports.