The first issue sounds like a bug in Joomla!'s com_installer. Please submit a bug report in Joomla! 1.6's bug tracker so that the maintainer of this feature can take a look, replicate the issue and fix it.
The second issue means that your server doesn't have the mcrypt PHP library installed or enabled. This is required for Akeeba Backup Professional to support secure (encrypted) storage of your configuration settings and for creating JPS (encrypted) archives. Akeeba Backup will still work with unencrypted settings; it's designed to fall back to a plain text storage format. However, if you can convince your host to enable the mcrypt extension you will ahve much better security of your settings in the unlikely event of a hacker trying to exploit a SQL injection vulnerability to dump your Akeeba Backup settings.
Nicholas K. Dionysopoulos
Lead Developer and Director
🇬🇷Greek: native 🇬🇧English: excellent 🇫🇷French: basic • 🕐 My time zone is Europe / Athens
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