There are many scenarios that can cause this error. Try each of the following steps that is specific to the scenario until the issue is resolved:

Change the regional settings to Date: MM/DD/YYYY and Time: HH:MM:SS

If the issue only occurs when the user double-clicks a shortcut to log into The Raiser's Edge:
  1. On the desktop, right-click the shortcut for The Raiser's Edge and select Delete.
  2. Click Yes to the prompt confirming you want to delete the shortcut.
  3. Recreate the shortcut for The Raiser's Edge.

If it only happens on one workstation, manually update/repair the workstation

If it occurs right after updating 
  1. Stop the database engine.
  2. Run setup.exe from the CD or deploy folder on the machine that houses Blackbaud Management Console selecting to Update/Repair the Blackbaud Management Console.
  3. Start the database engine..
  4. Log into updated workstation.

If it occurs for all users in specific user group, create a new user group with the same security rights and transfer all users in the old group to the new group. Delete the old group.

If it only occurs for one specific windows profile then recreate the problem user's Windows Profile.