[Hummingbird] Hummingbird Caching Old Posts As "New"

Hello,

We run a magazine site at http://spudsmart.com/ and started using Hummingbird as our sole caching plugin around September 11. Today is was discovered that (non-logged in) users saw the newest posts/articles on the homepage as September 11, regardless of what had been posted afterwards (probably a dozen articles or so). I believe that I had "page caching" enabled, could that be part of the problem?