the theme has to be *verified* OTS2.

I had this same problem.

OTS2, from what I gather, is a completely brand new standard.. so of course... there's bugs.

go to the theme download area, click browse, and sort by OTS2 themes. A highly recommended theme that only has one misconfiguration is Plastik II.

You have to open it up and change the LSmail settings, as far as everything else... it's the only theme that has seamlessly intergrated with my box.