We have seen strange things happening with Theme Builder and how it plays with PowerPoint 2010 (and PowerPoint 2011 for Mac). For some reason, Theme Builder creates THMX files that are not too well supported by the newer versions of PowerPoint. The solution is to keep a copy of older Theme aware versions of PowerPoint installed, and resave the THMX from within those programs!
Be aware that Themes saved in Theme Builder may not be compatible with PowerPoint 2010 and 2011.

