I am having the same exact problem with my 2003 manual transmission Subaru Forester (2.5 model, as well). Oh, and it has 74,000 miles on it. I, too, thought it was the CV joints. It just started doing this two days ago.
I took it the the shop today and they couldn’t locate the problem just by lifting it and looking at it (so I am doubting the CV joints). They told me to drop it by tomorrow morning and they are going to really investigate it. The first thing he said they would look at is the rear differential fluid.
I started looking here to get more info and discovered this post. I am curious if you ever found out what the problem was and how much it cost?
Thanks very much, I appreciate it!