I get server certificate errors routinely from USN sites. I've never used Chrome but have gotten them using both IE and Firefox. I'm not sure what causes it. My theory is that a lot of the sites are older versions that have been superceded, or free access is no longer available because of 9-11 related security issues.
In any case you've got a link to what is most likely a current site from a trusted source. That means you're relatively safe in going to the site. Does Chrome give you a choice to go ahead and connect anyway? The one that Firefox gives is very ominous and with good reason. If you are certain the site is safe however I would go ahead and use what's available to connect.
Alternately I'd try IE to see what happens. There are some sites that just arene't set up to work with non-MS browsers.
Good luck
