The Yahoo results are slightly different from my google search, so even if I don't find the painting in question, there's still much to enjoy.
Let me know if you find it somewhere on the web, and thanks for helping out!

I looked at that scene all over again just a few hours ago, and now I'm not so sure that it
wasn't
a Renoir (BTW, I love, just absolutely LOVE, Renoir's works! Monet, too, FWIW). The painting did have that "soft" style of Renoir, which would be in keeping with his Impressionistic sensibilites, and even if it was a "fake" copy of an actual Renoir painting that was just used as a movie prop, it was still a beautiful picture.
So, was it a copy of an original Renoir just used as a movie prop?? As of right now, I can't say because I haven't reviewed every work ever done by Renoir, but if I ever come across it, I will let you know.
Here's a gallery of many, many Renoir paintings, including many of his most famous works:
http://images.search.yahoo.com/search/images?_adv_prop=image&fr=yfp-t-501&va=renoir&sz=

I realize that it's not an original - that would be beyond crazy; But if it was a copy made from an actual Renoir painting I was interested in knowing the name of it, since he named most or all (?) of his work. If it's in fact not even a replica of his work, then I wonder why not, it would't cost them more to use a cheap copy of a genuine painting would it? However, do you know where I can find the "painting" (picture rather) on the web? I would like to see it again!

I don't believe that painting was anything actually done by Renoir (not even a "copy" which could be used - and scratched! - for the movie).
The painting was of a rather plump nude young woman, not totally unlike something Renoir might have painted in his time (he painted a number of nudes, many of them being young, plump women), but the style of painting was not very similar to Renoir's style. Also, I have looked at a large body of Renoir paintings, and I see nothing that is exactly "this" particular painting. I could be wrong, but I really don't think this was anything ever done by Renoir.
By the way, the painting made it into the "goofs" section, as the painting already showed signs of being torn or scratched by the cat before the cat actually slid down and scratched it with its claws.