I use Drupal 7.38 and Boost 7.x-1.0. According to Cron everything is up2date. I store my site at a (CentOS) NGINX-based shared hosting plan that seemingly does include UTF-8 encoding (my site is in Hebrew and the problem is language related). I have no idea if the following problem is a Boost bug or a fail, from my side, providing one of Drupal's encoding-related system requirements.
The Boost module is installed and working (verified it's work when visited root/sitename/cache...) but now, in the bottom of each non-English webpage, I get the following 2 errors:
Warning: Cannot modify header information - headers already sent by (output started at /home/user/public_html/sitename/includes/common.inc:2748) in drupal_send_headers() (line 1232 of /home/user/public_html/sitename/includes/bootstrap.inc).
PDOException: in dblog_watchdog() (line 160 of /ho/home/user/public_html/modules/dblog/dblog.module).
The exact whereabouts
These errors appear ONLY in non-English webpages... In English ones, they just don't appear... moreover, The cached webpage files that BOOST creates are named in Hebrew - i.e their file names are in Hebrew and actually resemble their H1. If I change the file name to an English one, and visit it from the site --- these errors no longer appear in it's bottom.
Maybe the server\Drupal\Boost fails to access the files correctly and and therefore prints these errors in their bottom. Note: It doesn't happen on a local Windows WAMP server, so it's likely the problem is in my online server and not in Drupal.