At a brief glance, the error message "link must be a full and valid URL" would appear to imply that
<![CDATA[[url]http://treble.lfhost.com/1024/pages.php?page=news&id=29[/url]]]>
is not a full and valid URL; perhaps it ought to be
<![CDATA[http://treble.lfhost.com/1024/pages.php?page=news&id=29]]>
or even just
http://treble.lfhost.com/1024/pages.php?page=news&id=29
(seeing as how it's not going to contain any embedded tags.)
In fact
The page linked to by the bit that says help next to the error:
If this is a link to a web page, make sure to include the "http://" at the beginning......The data in link elements must begin win an IANA-registered URI scheme
And yours doesn't. It begins with [url].
The second error message would appear to be saying that the <channel> element needs a <link> element of its own (this error message also has a help page associated with it that explains what it should link to).