Is an Archive Mailbox just a regular mailbox? Or is it special?

According to adobe's website http://www.adobe.com/products/flash-media-streaming/tech-specs.html FMS requires Red Hat® Enterprise Linux® Server 5.5 (64 bit) or Linux CentOS 5.5 (64 bit)

Most likely the problem is that the version of libcap in RHEL 6.2 is more recent and the FMS is not finding the file its looking for.

I recommend contacting Adobe's support to see if you can install it on RHEL 6.2 or you can try using an older version of RHEL in amazon. I believe they have AMI's for almost any version you're looking for.