Problems With Dynamically Checking Radio Buttons

I have a little checkbox that when checked is suppose to "check" a number of radio buttons.

Problem is I get a js error ("Object doesn't support this property or method") when I click the checkbox that calls my check all function.

HTML Code:
<tr bgcolor="#eeeeee" class="form_header">
<td align="center" valign="middle">Database</td>
<td align="center" valign="middle">Primary&nbsp;&nbsp;<input type="checkbox" name="checkPrimaryAll" onClick="checkPrimaryAll();" style="background-color: #EEEEEE;"></td> <--- This is the line in error
<td align="center" valign="middle">Backup&nbsp;&nbsp;<input type="checkbox" name="checkBackupAll" onClick="checkBackupAll();" style="background-color: #EEEEEE;"></td>
<td align="center" valign="middle">Remove&nbsp;&nbsp;<input type="checkbox" name="checkall" onClick="checkAll();" style="background-color: #EEEEEE;"></td>
<td align="center" valign="middle">Current DBA(s)</td>
</tr>

...

<script type="text/javascript">
function enableDisable(objectNme, myId)
{
var remCheck = document.getElementById(myId);

if(remCheck.checked == true)
{
eval("document.forms[0]." + objectNme + "[0].disabled = true;");
eval("document.forms[0]." + objectNme + "[1].disabled = true;");
}
else if(remCheck.checked == false)
{
eval("document.forms[0]." + objectNme + "[0].disabled = false;");
eval("document.forms[0]." + objectNme + "[1].disabled = false;");
}
else
{
alert("Error");
}
}
function checkAll()
{
var lng = document.AssociateDBAForm.remove_dba.length;
var select_all = document.AssociateDBAForm.checkall.checked;
var myForm = document.AssociateDBAForm;
var value;
for(var i = 0; i < lng; i++)
{
if(select_all == true)
{
myForm.remove_dba[i].checked = true;
myForm.checkall.title = "Unselect all rows";
value = myForm.remove_dba[i].value;
value = "ADD_" + value;
eval("myForm." + value + "[0].disabled = true;");
eval("myForm." + value + "[1].disabled = true;");
}
else if(select_all == false)
{
myForm.remove_dba[i].checked = false;
myForm.checkall.title = "Select all rows";
value = myForm.remove_dba[i].value;
value = "ADD_" + value;
eval("myForm." + value + "[0].disabled = false;");
eval("myForm." + value + "[1].disabled = false;");
}
}
}
function checkPrimaryAll() <--- This is the function it calls
{
var myForm = document.AssociateDBAForm;
alert("myForm " + myForm);
var lng = myForm.elements.length;
alert("lng " + lng);
var select_all = myForm.checkPrimaryAll.checked;
alert("select_all " + select_all);
for(var i = 0; i < lng; i++)
{
if(select_all == true)
{
myForm.checkPrimaryAll.checked = true;
myForm.checkPrimaryAll.title = "Unselect all rows";
thisElement = myForm.elements[i];
if(thisElement.name.substring(0, 4).equals("ADD_"))
{
thisElement[0].checked = false;
}
}
else if(select_all == false)
{
myForm.checkPrimaryAll.checked = false;
myForm.checkPrimaryAll.title = "Select all rows";
thisElement = myForm.elements[i];
if(thisElement.name.substring(0, 4).equals("ADD_"))
{
thisElement[0].checked = true;
}
}
}
}
</script>
As you can see I tried putting in alerts to try to debug, but it never hits them, even if it's the first line in the function.