Drupal 6.x is caching custom 'page not found' page and replacing it with custom front page

The Drupal site is getting some page not found errors everyday and after sometime like a day or two, the custom error page 'page not fou开发者_高级运维nd' kicks in instead of the front page (all other pages would still work). And when I flush all the cache in Drupal, the front page comes back alive again immediately. And this happens just for Anonymous users only. I went through the watchdog and all I can see is only a couple of 'page not found' messages at the end for a day.

Is the front page created with Panels(or just ctools page manager) ? Then, in addition to setting front page in ctools interface itself, set the same value in Site Information admin page. It solves the problem in most cases.

If you have page caching(using core, boost or anything else) turned on, turn of ctools' caching mechanism. Using both will confuse the menu system. This is the reason for most 404 errors. You could find many similar threads in drupal.org as well.