Hello,
Could you try creating a package with Basic Content option instead of All content and check.
Symantec is currently investigating this issue.
As of now, I would recommend you to Uninstall and Re-install SEPM 12.1 RU1, which would resolve the issue and you would be able to create the client packages.
Again, make sure you have created a case with Symantec Technical Support as well.
I would suggest you to open a Case with Symantec Technical Support.
You would have to call symantec or log a web case.
QuickStart Guide - Create and Manage Support Cases in SymWISE
http://www.symantec.com/docs/HOWTO31132
How to update a support case and upload diagnostic files with MySupport
http://www.symantec.com/docs/TECH71023
Hope that helps!!