Errors after upgrading to 3.5.3

I had the same problem. Updated WordPress to 3.5.2, get the “error”.
Manually updated Better WP Security to 3.5.3 through FTP, problem persists. I deleted it manually and restored the .htaccess, and I’m up again.
Then I tried a clean install of Better WP Security, get the errors. Tried clearing cache, no help. I have my admin page rewritten with the default setting.

I’d like to use the plugin but now I fear all of my sites will be this fragile.

Hmm, everything is working fine again, upon another attempt at installing the plugin. Sorry, can’t reproduce it… but check Cache, check the .htaccess that you are not banning yourself, and FTP to delete the files and go into WP plugins where it will say “plugin is deactivated” because the files were deleted, and click around until that message goes away, then clean install.

I had the same problem too. After updated to WordPress 3.5.2 my website temporary blocked me twice.

After inspection I found my site generated too many 404 errors which the IP is my server’s IP. And on my Lastest Visitor (CPanel) log I saw these message were being repeated many times:

/not_found?step=1
/wp-admin/upgrade.php?step=1
/wp-cron.php?doing_wp_cron=1372400086.9695360660552978

I think this plugin blocked cron process for upgrading WordPress. I tried to reinstall this plugin as being suggested by pbure, the issue solved.

Thanks pbure.