If you recently installed a DITA2Go upgrade or beta version, after you run DITA2Go, check to make sure the latest version was actually used to produce HTML output. Windows sometimes caches DLLs, and does not always use a newly replaced DLL until after the system is rebooted.
Open an HTML output file and look at the fourth line. You should see something like the following:
<!-- generated by DCL filter dwhtm,
Ver 4.0 m193 h272a -->
The last two entries identify the build numbers of the DITA2Go drxml.dll and dwhtm.dll components that were used to create the HTML file. See §A.1.5 Check your version of DITA2Go.