Have you noticed any compatibility issues with WordPress version 3.7.1? After updating to that version (failed automatic installation; had to install manually twice and disable all plugins before it would work), I am getting a message that the Ryu theme (and one other I have installed but am not currently using) is broken, "stylesheet missing." I'm using a child theme, which is available but obviously not working in the absence of the parent. Downgrading back to 3.6, the theme works.
Via FTP I can see that the parent theme is there and intact, with stylesheet. Opening the stylesheet, all info is there too. I cannot delete the folder or its contents manually via FTP, nor can I overwrite it. I cannot update or reinstall from within the Dashboard either. Twentythirteen theme works fine (ugly, but functional).