I have a few form elements that when viewed in Opera do not allow entry of data. But some do. Any reason why this is happening? The first input field doesn't allow any input in Opera, but the second input field does.

HTML Code:
<input id="_id163:txtinzip1" type="text" name="_id163:txtinzip1" class="inputFixed" maxlength="5" onkeypress="return numbersonly(this,event)" size="5" />
<span id="_id163:txtoutHyphen3"> - </span>
<input id="_id163:txtinzip2" type="text" name="_id163:txtinzip2" class="inputFixed" maxlength="4" onkeypress="return numbersonly(this,event)" size="4" />
On a possible related note. We are using javascript for numeric entry. So it may be possible that this javascript is causing issues with Opera?

HTML Code:
// numbers
else if ((("0123456789").indexOf(keychar) > -1))
   return true;
else
   return false;
}
function lettersonly(e)
{
var key;
var keychar;
if (window.event)
	key = window.event.keyCode;
else if (e)
	key = e.which;
else
	return true;
keychar = String.fromCharCode(key);
keychar = keychar.toLowerCase();