Can not access admin links I have encountered a weird problem in Drupal 6 in the recent days: I can log in as admin but none of the mysite.com/admin/* links work from GUI. 

I still can use drush to enable and disable modules and do other administrative tasks but can not do the same from the admin menu. 

None of the other aspects of the site are affected. I cleared all cache, updated the database, performed cron (using drush), and restarted all servers. Alas, no effect. The log messages are not helpful either.  I'm really perplexed and appreciate your help.
It turned out to be a problem with nginx/php5-fpm settings that timeout prematurely. When I use apache (using another port) the problem does not exist.