Should you receive this error message upon opening a Task Sequence, you must go to the TaskSequenceProvider.log found in \\siteserver\sms_”Sitecode”\Logs, and check for the specific error there.
If you get errors like:
Failed to load class properties and qualifiers for class BDD_UsePackage in Task Sequence
Failed to export task sequence to XML 0x0041002
The problem is clearly Microsoft Deployment Toolkit integration (it used to be called Business Desktop Deployment – BDD)
Simply uninstall the MDT integration, and then add it again. You might want to restart the server (to make sure all services are running properly), but it should not be necessary!
You might also receive an 0x80041006 error, which resolves to some out of memory WMI stuff. If this is the case there is this excellent post by the SCCM Team providing a solution. http://blogs.technet.com/b/configmgrteam/archive/2011/01/18/task-sequence-editor-too-many-steps-issue-and-solution.aspx