As TMZ reported, the Estate has been sued by Nederlander Presentations on Thursday.
What they didn't know of that the Estate has been sued by another company the same day. Seven Echols (dba Security Measurements) filed a claim on June 17, 2010. Echols' company provided security for MJ in Las Vegas years ago.
It seems that the creditors got impatient and launched legal actions instead of waiting for the Estate lawyers.
PS.: I have received some comments here in the blog, that I just answered.