Upgrade 1.6 to 1.9, used a theme based on RWD and OPC not working

[Lee_Chilli]

I've been working on upgrading my website and got it to 1.9.

I changed the whole theme of the website to use a clone I created of the RWD to change it to how I need it to look and feel and now come across the newest people. 

Once checkout I can choose to login or be a guest then enter my billing information, if I choose same as billing nothing happens, if I choose different address it moves to to delivery address but the box is completely empty (http://magento.stackexchange.com/questions/75110/onepage-checkout-uncaught-typeerror-cannot-set-prop...

Any help with this would be great

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Update:

I've still been working on this and had someone suggest on Magento stack that it could be an issue with the theme so I've reverted back to RWD and also reuploaded a clean copy of this theme but still having the same issue

[Lee_Chilli]

Still working to resolve this issue with no luck. Would any more information be useful to help work out the problem?

[Lee_Chilli]

Sorry for replying to myself, Is there anything missing which could help others help myself? I'm still having this issue and unable to resovle it through means currently found on other stackoverflow questions. 

[Lee_Chilli]

I've still been working on this and had someone suggest on Magento stack that it could be an issue with the theme so I've reverted back to RWD and also reuploaded a clean copy of this theme but still having the same issue