When I log out, then go back to a page I was previously viewing when logged-in, it displays as if I were still logged in. Disabling Hyper-Cache-Extended fixes the problem, but that's a bit drastic.
In cache.php, replacing
if ($if_modified_since >= $hc_file_time)
if ($if_modified_since == $hc_file_time)
also seems to do the job, although I haven't tested exhaustively. I think the browser had a cached version of the logged-in page that was newer than the HCE cached version, and HCE was telling it that its version was OK - am I right? I'm not sure I understand why the browser was caching anything, though. Happened with firefox 8 and chrome 15.