Nope. Google Reader is fine. But the RSS entries that it's displaying sometimes other resources from the original blogs. For videos or click tracking, this sometimes is JS.

Before the change, it just put the browser into mixed-content-mode, but now it does that and in addition it disables loaded JS.

I think it should block it without the error message though.

Their cert is fine, it's just that the page generally has to load content from external, untrusted sources to do what it does.