Windows 7 - Win 7 x64 conflicts with Firefox 10

Hi, I have recently updated to a Win 7 x64 bit pc and some of my usual sites in Firefox are not working properly. The links in all emails lead to a blank tab rather then the link, multiple parts of ancestry.com won't work. I've corresponded with ancestry.com and I've checked my settings regarding blocked sites and pop ups (as per their help team) and made sure I have the latest Java. I checked my add-ons. Any ideas please? It all works on my Vista laptop, so I'm pretty sure it's a Win 7/Firefox problem. The option to tick Java (JRE) in Internet Options/ Advanced Tab doesn't exist. (This was recommended by Ancestry, but I don't HAVE IT. Thanks