The Complex Script Font appears when there is an editing language which requires it such as Arabic in the Word's settings. To remove it, go to File -> Options -> Language and remove from the list of Choosen Editing Languages any Editing Language requiring
the use of Complex Script Font (like Arabic) then restart Word.
It's also possible that parts of your document use this language; even if it's only for a few blank spaces here and there; therefore you should also remove the language formating for all of your document. Select All of your document then go to Language
-> Set Proofing Language... -> Mark Selected text as: -> chose English.
In this same dialog box, you should also set English as the default language used for Proofing (click on the "Set As Default" button after having highlighted English and it's also better to uncheck the "Detect language automatically" option. Save your document,
close Word and when Word ask you if you want to save the Normal.Dot file, say Yes.
Finally, you should also uncheck the option "Automatically switch keyboard to match language of surrounding text" in Options -> Advanced -> Editing Options.
After all this, you shouldn't have any more problem with the Complex Script Font features of Word.