Can't start up "Virtuoso Documentation" window

Hi Andrew,

     I can't start up "Virtuoso Documentation" window, it shows no errors & no warnings.

 The function called is  ddsOnLineHelp('main) in VLS L 

                                  hiHelp('window "virtuosoLibrary" getCurrentWindow() t) in VLS XL 

Then there is no any GUI shows up. Is there any solution for this situation?

Thanks in advance.