Patch 5.2.0j Edit
Patch 5.2.0j is the unofficial name for the patch build 16826 that came out about 2 weeks after the unofficially named "Patch 5.2.0i" build 16769. There is no info on this patch build and there has been no official acknowledgement of the release of this patch build. This client could correspond to the April 9, 2013 slate of hotfixes. It isn't clear why a client patch is needed.
See also Edit