Surely not! Scrivener wants to correct ‘vigorous’ to (eeep) ‘vigourous’!
Weird, I get that too. It is an antiquated form as far as I know, so I am not sure why it is recommending it. But it isn’t really a Scrivener bug. Try it in TextEdit, you’ll get the same thing.
Amber,
I thought you lived in Portland. What’s with the “favourites,” used in another post?
You know, we extract a tea tax from Limeys who’ve snuck down from Vancoover.
Droo
I’m Irish.
I’m confused. I know it is a state but I am not sure in what country.
So the Irish prefer US to UK spelling … I didn’t know that! 
Vigourous is incorrect in British English too. One of our many wacky spelling inconsistencies - “vigour” becomes “vigorous” (which is underlined as I type this in Safari). It seems that OS X cannot spell this word correctly…
Something else I didn’t know … I must educate my dictionary too!
Mark
It’s effin ineffable. And vigourous isn’t correct in any variant of English unless the year is 1356.
Ah … perhaps that explains it! I’m rigourously stuck in 1356!
I’ve just looked at my Shorter Oxford Dictionary (1991 reprinting). According to this, both vigour and vigorous are Old French. I’m not a student of linguistics, but I’ve come across a few cases recently in which British spellings or pronunciations come from Old French (for example, our pronunciation “fillett” rather than “feelay”, which latter is [roughly] the modern French pronunciation). If I’m not mistaken, the pronunciation “Pariss” rather than “Paree” is also a preservation of the Old French version. So, as so often, it looks as if it’s all because of the Normans.
Best wishes,
Martin BB.
Interesting point. Now I am inclined to examine all manner of place names and such for evidence of drift and stasis. I wonder if it is reproducibly so that when a sponge language acquires a foreign word, that word remains more resilient to change than the word in its original tongue; if the peoples who have acquired it are less inclined to let it drift out of “respect” for its supposed external status. Would the sponge language then become a bit of a locking mechanism, drifting through time and periodically freezing the state of vocabularies outside of its nets? Hmm.
About thirty years ago, I went to Highgate cemetery in London with a Polish friend to visit the tomb of Karl Marx. He noticed a number of gravestones belonging to Polish immigrants and commented on the fact that they used rather old-fashioned Polish. His observation was that the migrants, no longer being in direct contact with their home country, had been unaware of changes in the language, and had therefore carried on using the Polish they had brought with them. As I say, this is not at all my field, so I don’t know if this is what usually happens. It would seem logical to me that languages should drift apart where there is no contact, and drift together where there is. There also seems to be a process whereby words fall out of use and then get re-introduced with a different pronunciation or meaning. Dryden wrote the word ballet as “ballette” which would seem to suggest that he pronounced the final consonant (reflecting the Italian “balletto”, from which it originated). If we now say “ballay”, I suspect it is because the modern “art” dance form only became prominent in the 19th century as a largely Russian and French phenomenon, and so the word got taken into English a second time with a new pronunciation. But I’m only speculating.
Best,
Martin.
Yes, this is a known effect on languages. For example, I’ve read that afrikaans in south africa sounds humorously old-fashioned (or childish, depending on who you ask) to the Dutch, whose ancestors colonized the area a while back. You know, before those johnny-come-latelies who called themselves the british empire figured out ocean travel. 
A small population separated from the main population of that language tends to change their patterns of speech more slowly. Which leads to things like my mom’s cousins telling her that she sounds like their parents instead of the others in her generation…