So I am having the same problem. Every time the EC2 reboots it goes back to the generic EC2 ip for magento. This causes all sorts of problems.
What have I tried (yes all in combination). Editing the .htaccess, the database and removing any mention of the old one and placed in the new one, cleared all cache, and renamed updateip. Still same issue.
Is there something I am missing?
I am using the ami-c31e53aa and it seems this one has all sorts of problems or Bitnami made lots of changes to files and locations (many items are missing, have different names, or different locations than indicated in most of the help wiki's)