Have you seen 
http://backuppc.wiki.sourceforge.net/Install+Backuppc+with+Lighttpd

I did not have any serious problems making things work (Mandriva 
platform) with lighttpd (and I needed also webdav in order to get a 
foxmarks server).

In case that helps, here is the server definition that I needed to add 
at the end of /etc/lighttpd/lighttpd.conf

$HTTP["host"] =~ "^pcjuergen($|.unige.ch)" {
     $HTTP["url"] =~ "^/backuppc($|/)" {
         server.document-root = "/var/www/backuppc"
         alias.url = ( "/backuppc" => "/var/www/backuppc" )
         dir-listing.activate = "disable"
         index-file.names = ( "BackupPC_Admin.cgi" )
         $HTTP["remoteip"] != "127.0.0.1" {
             auth.backend = "htpasswd"
             auth.backend.htpasswd.userfile = "/server/www/passwd/backuppc"
             auth.require += ( "" => (   "method" => "basic",
                                         "realm" => "BackupPC",
                                         "require" => "valid-user" ) )
         }
     }
     $HTTP["url"] =~ "^/webdav($|/)" {
... snip ...
     }
}

------------------------------------------------------------------------------
Apps built with the Adobe(R) Flex(R) framework and Flex Builder(TM) are
powering Web 2.0 with engaging, cross-platform capabilities. Quickly and
easily build your RIAs with Flex Builder, the Eclipse(TM)based development
software that enables intelligent coding and step-through debugging.
Download the free 60 day trial. http://p.sf.net/sfu/www-adobe-com
_______________________________________________
BackupPC-users mailing list
BackupPC-users AT lists.sourceforge DOT net
List:    https://lists.sourceforge.net/lists/listinfo/backuppc-users
Wiki:    http://backuppc.wiki.sourceforge.net
Project: http://backuppc.sourceforge.net/