Feed does not validate

[helpy]

http://feedvalidator.org/check.cgi?url=h...cation.php

[edit]
Because of new posts, the feed with the first 15 topics does validate. Check this:
==> http://feedvalidator.org/check.cgi?url=h...limit%3D50
or this:
==> http://feedvalidator.org/check.cgi?url=h...limit%3D50


The error is caused by the feed entry of this topic:
==> http://community.mybboard.net/showthread.php?tid=17516
[/edit]