IE9 issues with magento checkout disabled credit card fields fix

The fix:
Browse to your /skin/frontend/..template folder (if you’ve got one, if not, browse to the /skin/frontend/default/default/js/ folder). Open up the opcheckout.js file. Around lines 641 AND 647, (inside the switchMethod function), replace :

1	var elements = form.select('input', 'select', 'textarea');

with

1	var elements = form.select('input').concat(form.select('select'), form.select('textarea'));

These 2 lines should fix your IE9 issues, as well as be compatible and work with Chrome/Firefox, earlier builds of IE, and others.