Javascript validation works fine in chrome & F/fox but not in IE, why?

I have a web page that has javascript validation which works fine in both Chrome & firefox but does not work correctly in Internet Explorer. There is a radio button field that when checked requires further validation that a new address is entered, when all address fields are entered it should submit, only then. IE will not do this even though it validates . I have copied the code in below.
Can anyone please help & shed some light on this for me?

Thanks in advance.
Agni

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