Issue with ’ Char ’ in permalinks

Hi All,

I have updated my wp site from 2.9.2 to 3.5.
After few days looking at webmaster tool I saw 404 errors quickly rising.
Checking them I seen that most of them are related to tag pages which “title” contained char %E2%80%99 ( or ” ’ ” in browser ) like this /tag/antropologia-dell%E2%80%99alimentazione.
Looking in analytics I see that those pages where regularly visited before update.
Now I still see tags properly related to posts but vlicking on them I actually see 404 page.
Any Idea about how this happened and how to solve?

Thanks!

Andrea