I have a rebuild kit for the rears sitting right in front of me. Direct from the factory, I used a kit on my car and it worked perfectly. Let me know if your interested.
I've got a rear caliper rebuild kit laying around if you're intersted. Did mine, it's very easy, and solved my problem of a seized caliper. Let me know if your interested.
Make sure the springs are seated correctly. You'll have to pull the wheels, and check that the bottom of the springs are sitting in the correct position on the spring perch(where it sits on the strut). You more than likely should just be able to turn the spring by hand if it's not in the right...