JavaScript - Help Me, Some Genius, Please!!!

I am getting an error, in IE only (7 and 8). Firefox, Safari and Netscape work fine.

The problem is with older code, that I have not worked with. (Owner just noticed it, so now I am stuck fixing it.)

The code is bascially a dynamic text box, that when a user starts typing in a product name, it displays a drop down list that the user can use to select a product. Once they select their product, a second drop down box displays the various sizes and prices (i.e. Small - $7.50, Medium - $8.50, Large - $10.50.)

The error I am seeing in IE is the following: 'name' is null or not an object.

Here is the actual select boxes code:

Code:

<input id="myInput" type="text" style="height:18px; width:190px;" value = 'Type To Find Product' onfocus="this.form.myInput.value='';this.form.products_id.value='';this.form.cart_quantity.value=1;">
	
	
		<div id="myContainer"></div>
	</div>

</div>

<div class="back" style="margin-left:20px;">
	<div class="orange" style="line-height:18px;">Size</div>	
	
	<select name="id[<?php echo WEIGHT_OPTION_ID; ?>]" id="attrib-<?php echo WEIGHT_OPTION_ID; ?>" style="width:114px;height:20px;">
		<option value="">Select Product</option>
	</select>
</div>

The actual error is occuring here - again only in IE - firefox and other browsers work fine.
Code:

var handleSuccess = function(o){
				var test=eval(o.responseText);
				
				if(test != undefined){
					removeAllOptions(selectbox);
					addOption(selectbox,'Choose Weight','');
					for (var i = 0; i < test.length; i++){
						 addOption(selectbox, test[i].name, test[i].id);  -  here is where it throws an error 					}
				}else{
					removeAllOptions(selectbox);
					addOption(selectbox,'Select Product','');
				}
				
			}

For the life of me, I cannot figure out how to solve this. And I am forced to work until it is fixed, which could be days. No weekend for me unless I can figure this out, or unless someone has a clue that I am missing.

Thank you to whomever can help me!!!!!!!!