Page Not Found for anonymous (clear cache fixes it) I'm getting reports from users that clicking a link gives them Page Not Found.


These are anonymous users.
Page caching is turned on (but not aggressive)
I log in, the page works.  I log out, the page does not work.
Three reports of unrelated pages in the past week (but all were different node types)
Clearing All Caches fixes it.
I could be wrong about this (because I didn't think to check until after I cleared caches), but I think it's returning error 406 in Recent Log Entries.


How can I begin to troubleshoot this?
Ask your sysadmin about the health and size of cache tables. Being logged in bypasses page cache. Clearing cache truncates them. Last time I've encountered similar effects, they were caused by a bad sector on server's HDD - when cache table grew enough to start using it, caches got all messed up. It was most visible with page cache.