You might run into problems editing groups and schedules from the project browser or opening old files. This occurs in Revit 2008, 9.1, Structures 4, etc. If you encounter a "failed to open" or "unspecified error encountered" message than set your pc clock to a month other than January and perform the same task.
Watch the following video or scroll down for the step by step how to:
- Double click on the system time shown in the system tray located at the lower right corner of your windows desktop.
- When the system date and Time Properties dialog box is displayed change the Month to anything other than January
- Click the Apply button then click "OK"
- Open your legacy file or perform your edit within Revit as necessary
- The system clock may set it self back automatically if you are controlled by group policy otherwise follow these steps in reverse to reset the date manually.