javascript toggle not working in mac safari

[Olona]

can anyone help me in identifying why this code doesn't work in mac safari? it also doesn't work in firefox 1.04 -- but as far as i have tested, it works in all other browsers. thank you much-

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<td><input id="need_pickup" name="need_pickup" type="checkbox" onClick="togglePickupType()" tabindex="18"/> Need a Pickup:</td>
<td id="pickup_cell">
<select id="pickup" name="pickup" tabindex="19">
<option value="1">CD</option>
<option value="2">Drawings</option>
<option value="3">Drawings with Handtruck</option>
</select>
</td>
-----------------------------------
<script type="text/javascript">
togglePickupType();
</script>
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/*toggle visibility of the type of pickup input*/
function togglePickupType() {
if(document.getElementById('need_pickup').checked == true) {
changeElemVisibility('visible', document.getElementById('pickup_cell'));
}
else {
changeElemVisibility('collapse', document.getElementById('pickup_cell'));
}
}