[рони]

monolithed,
Возможно TC всего лишь дубликат ...

<script type="text/javascript">
var TextForR = {
    'query_1' : 'Текст 1',
    'query_2' : 'Текст 2',
    'query_3' : 'Текст 3'
};
var TextForR2 = {
    'query_1' : 'Текст 11',
    'query_2' : 'Текст 22',
    'query_3' : 'Текст 33'
};
function foo(r) {
    if (r && r.value && TextForR[r.value]) document.SetQuery.query_text.value = TextForR[r.value];
};
function foo2(r) {
    if (r && r.value && TextForR2[r.value]) document.SetQuery2.query_text2.value = TextForR2[r.value];
};
</script>
<form name = "SetQuery" action = "queries.php" method = "post">
        <textarea  name="query_text"></textarea>
        <input type = "radio" name = "query" value = "query_1" onclick="foo(this)">Запрос 1
        <input type = "radio" name = "query" value = "query_2" onclick="foo(this)">Запрос 2
        <input type = "radio" name = "query" value = "query_3" onclick="foo(this)">Запрос 3
</form>
<form name = "SetQuery2" action = "queries.php" method = "post">
        <textarea  name="query_text2"></textarea>
        <input type = "radio" name = "query" value = "query_1" onclick="foo2(this)">Запрос 1
        <input type = "radio" name = "query" value = "query_2" onclick="foo2(this)">Запрос 2
        <input type = "radio" name = "query" value = "query_3" onclick="foo2(this)">Запрос 3
</form>

P.S. onclick надёжнее onchange ...