Supplied argument is not a valid MySQL-Link resource

Jeg får en lille fejl...Hvorfor???
Warning: Supplied argument is not a valid MySQL-Link resource in /home/gunnar/public_html/funktioner.php on line 14

<?
include (\"forbindelse.php\");
function opdaterikkeafhentedebilletter(){
$dato=(date(\"Y-m-d\"));
$quarter = date(\"Hi\", mktime(date(\"H\"),date(\"i\")+15,0,1,1,2000));
$result4=mysql_query(\"select * from forestilling\");
echo \"<table align=center border=1 cellspacing=0 cellpadding=0>\\n\";
while ($x_row = mysql_fetch_array($result4)){
if(($x_row[dato]==date(\"Y-m-d\")) and ($x_row[tid]<($quarter))){
$result5=mysql_query(\"select * from sal1 where forestillingid=$x_row[id] \");
while ($z_row = mysql_fetch_array($result5)){
echo\"$z_row[status]\";
if ($z_row[status]!=\'ledig\' and $z_row[status]!=\'solgt\'){
(linie14 starter her!)
$query7 =\"update sal1 set status=\'ledig\' where id=$z_row[id]\";
mysql_query($query7,$c) or die (\"Kunne ikke tilføje data\".mysql_error());           
}//if
}//while
}//if
}//while
}//function
?>