I think there are two things going on here. The first is that I introduced a bug into 0.6.22 that affects backups to the bucket root:
In retrospect, that was pretty large omission in my testing, but I always backup to subdirectories in the bucket and missed it. So I feel pretty silly about that one.
The details are beyond the scope of this man page, but it is important to know that your bucket must not contain upper
case letters or any other characters that are not valid parts of a hostname. Consequently, for reasons of backwards
compatibility, use of subdomain based bucket addressing is not enabled by default.
I'm surprised that you haven't run into certificate errors.
The main problem is that bug, though. The workaround would be to downgrade to 0.6.21, use a bucket subdirectory or apply a patch.
-lee