There have been a couple bugs revealed with Revit since the calendar changed to January 2008. If you are trying to open a file that was last saved in 8.1 (or earlier) you are probably getting a "Failed to Open" error message. Or, if you are editing a group, saving a view, group or schedule out to an external file, you are probably getting an "Unspecified Error" message.
Autodesk was made aware of this problem and today released this responce on their Service and Support page....http://usa.autodesk.com/adsk/servlet/ps/item?siteID=123112&id=10458150&linkID=9243099
This issue will only occur in January, 2008. As of February 1st, 2008, this issue will no longer occur.
To work around this issue
1. On the Start menu (Windows), click Settings > Control Panel.
2. In Control Panel, double-click Date and Time.
3. In the Date and Time Properties dialog box, on the Date and Time tab, change the month to any month other than January.
4. Click OK.
5. Perform the required task.
6. Change the system date back to the current date.
Warning! Changing the system date can impact other software and utilities on your computer. Please contact your system administrator before making these changes.
So, if you are one of the lucky ones that can actually change the month or make any change to your clock settings, you can get around the issue. But, if your IT department/person has locked everything down tight, you'll have to get permission from them or have them change it before you can do any of the tasks that are affected in the month of January!