My b2evolution Version: Not Entered

I'm pretty sure that I have an Apache2 setting wrong, but was hoping somebody here could give me some advice.

When I try to access a Single Post URL, I get errors (which vary depending on how I've set Single Post URLs to work).

If I have them set as "Post ID" or "Post Title", I get a weird "Redirect Loop" error.

All the other ULR settings give me a "Not Found" error, saying it can't find the file "/usr/share/b2evolution/index.php"

I am using the .htaccess file and have uncommented the lines:
RewriteEngine On
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule ^ index.php

I also have tried uncommenting the "Clean URL" line "AcceptPathInfo On".

I'm sure I've got some Apache2 setting wrong with my Debian etch setup.

Can someone point me in the correct direction? TIA!