SYMPTOM:
A user gets the following error immediately after logging in to Strategy Web 9.4.1 and above:

An error has occurred on this page. Your request could not be processed. Please try again. If the problem persists, contact the Administrator. The object does not exist in the metadata.

ACTION:
The user preference "Default start page" has to be changed to an existing object or "Home". For more information on how to set up this preference, refer to tech note KB12226: How to set a report as the default start page in MicroStrategy Web
Note: this setting also exists at the Project Defaults level. If every user has the same issue, this may have been set at this level instead. Changing the preference at the Project Defaults level does not override the setting at the user level.