Undesired caching

Hello,

I manage several WordPress blogs, all of which are currently running WordPress 2.6. One of them, though, seems to force itself to be cached in the user’s browser so that they do not see new posts until they click Refresh. There is not a caching plugin enabled on this site, and though there was one at one point it has been deleted for some time.

Is there anything I can do to force new posts to show up? I’m a bit at a loss, as I’ve never run into this with other WordPress installations before.

Thanks,
Jonathan