Okay. I reverted to an older template that does not include Haloscan or Echo. We are now using Blogger's native comments. Not quite as powerful, but at least they work.
Comments are unfortunately no longer threaded, but they are all there and easily accessible.
I have also removed the JS-Kit "Recent Comments" widget until I can either fix JS-Kit or migrate to a service that actually works.
At least it's easy again to post and read comments.