Autodesk products run on Microsoft operating systems. To reduce development costs and to be able to provide solutions in a more timely fashion, Autodesk products rely on Microsoft technologies rather than "reinventing the wheel" on our own at Autodesk.
Although many customers consider Internet Explorer just a browser, it is more than that. In addition to the browser executable, Internet Explorer consists of many supporting libraries that are related to functionality as commonplace as the opening and saving of files. Internet Explorer is really part of the operating system. It affects how HTML pages are browsed on the internet or how HTML is used as part of menuing systems for Windows applications.
When an application is installed on a Microsoft operating system, the program and libraries that support it are stored on the computer's hard drive. It is quite common for a new version of an existing library to be installed. This happens because the application being installed relies on functionality that is only found in the newer version of the library. In theory, this approach provides the best of both worlds: the updated library supports the new application, and old applications continue to work because the new library is backward compatible. As such, even when the application is uninstalled, the newer supporting libraries are left in place. Installers check library versions to ensure that an older library does not replace a newer one. The libraries never go backward and lose functionality.
As originally released, Autodesk DWF Viewer and Autodesk Design Review are not compatible with the Microsoft Internet Explorer 7. These three Autodesk applications use HTML as part of their menuing interfaces and are impacted by Microsoft Internet Explorer 7 operation. Uninstalling Internet Explorer 7 and reverting to Internet Explorer 6 does not restore Autodesk functionality, because the supporting libraries from the Internet Explorer 7 Release Candidate are left in place.
Microsoft will make Internet Explorer 7 available as a mandatory security update. Today must really be Friday the 13th. Autodesk customers are encouraged to obtain and apply the hotfix for this issue.