I started a topic about this a month or so ago. Many people have noticed the same thing happening, so it's definitely not rare.
I chalk some of it up to testing. Some of the results I have been seeing on .com lately were basically taken from the other Gs.
I also think it has something to do with some sort of filter. Perhaps synonyms or something else.
So let me ask you this, are you well ranked in other English Googles or only non-English?