UNION : supplied argument is not a valid

FEJL:
Warning: mysql_fetch_array(): supplied argument is not a valid MySQL result resource in /home/domain/public_html/templates/config.phtml on line 195


$resforum = mysql_query("
(SELECT * FROM unihelp )
UNION
(SELECT * FROM help )
UNION
(SELECT * FROM trick )
UNION
(SELECT * FROM ghelp )
UNION
(SELECT * FROM frehelp )
UNION
(SELECT * FROM forse )
UNION
(SELECT * FROM xl )
UNION
(SELECT * FROM japt )
UNION
(SELECT * FROM ht )

ORDER BY datestamp DESC limit 10");

$forum = $forum . "<table width=100% BORDER=\"0\" CELLSPACING=\"0\" CELLPADDING=\"0\">";

LINIE 195: while($rowforum = mysql_fetch_array($resforum))

{
$forum = $forum . "<tr><td height=20><p><a href=../se_child_forum.phtml?forum_id={$rowforum["forum"]}&id={$rowforum["thread"]}>{$rowforum["subject"]}</a></td></tr>";
}
$forum = $forum . "</table>";

}

Det mærkelige er at det kun er nogen af tabellerne den går kold over. er der noget jeg skal være opmærksom ved i tabellerne? når man bruger UNION.