I had this problem with extras-devel and extras-testing since 1.2 as well. I fixed it by editing all of the repositories, changing the Distribution field from "fremantle-1.2" to just "fremantle" and everything worked again.

I guess they were supposed to give 1.2 some special treatment, probably because of the new Qt libraries, but apparently they never did get around to creating the fremantle-1.2 directory structure on the server.