The 502 error message can appear during program installation, while a Apache-related software program is running, during Windows startup or shutdown, or even during the installation of the Windows operating system. Microsoft is constantly updating and improving Windows system files that could be associated with Error 502. Sometimes resolving your Runtime Errors problems may be as simple as updating Windows with the latest Service Pack or other patch that Microsoft releases on an ongoing basis. For more info on how to fix excel errors here.