Try this, sometimes PHP doesn't parse information inside " correctly, especially when it's arrays.
$sql = "INSERT INTO table SET";
$sql .= "field1 = '".$sArray[$a][termid]."', ";
$sql .= "field2 = '".$sArray[$a][termnumber]."' ";
$sql .= "WHERE field3 = '".$sArray[$a][termkey]."' ";