Microsoft word

You know you're a foreigner when you get intimidated by the green line under a sentence in Microsoft Word. That line is telling you that what you just wrote is not considered proper in English. Just not correct enough for Uncle Sam or Bill Gates.
So today as I was typing a report, the line came under a sentence that I found perfectly normal and I began wondering what was wrong with it. If this was in French, I would have imposed my will to the software, telling it to go to hell and proceed but this is English. Not mine yet.
So I sweat for about 10 minutes trying to find and fix the mistake. A verb? A noun? An invisible extra space? I finally found it. The sentence was in the passive voice. A perfectly fine form of speech in French, an unacceptable treason of the energy of the language in English.