Sharethis buttons are not loading some times

Can you please provide us your site URL so that we can take a look. Please note that such problem occurs either when something is blocking the ShareThis buttons to load or due network issues.

I'm getting similar results. Rebuilding the registry with 'drush rr' allows the buttons to load, but clearly I can't keep doing that.
Here's a page where this is happening:
http://dev.familytravelforum.com/content/12104-pennsylvania-apple-farms-...

I have the same behavior.

The same page opened in the same browser (registered user and incognito session) gives different results.
Yes, clearing the cache helps but this is not a proper solution.

I noticed the bug doesn't depend on network. The js file not queried by the browser in case when the widget is absent. The declaration for this js is not present in HTML source. No share buttons - no <script src="http://w.sharethis.com/button/buttons.js"></script> in HTML source.

It seems to me turning off the 'Cache blocks' on performance page (admin/config/development/performance) fixes the issue.

But it's better to set this in the code (in sharethis.module, in function sharethis_block_info()):

    'cache' => DRUPAL_NO_CACHE,

instead of

    'cache' => DRUPAL_CACHE_PER_PAGE,

Remember to clear the cache if you modify the function sharethis_block_info() to let the changes take affect.

Be aware that in some cases your browser will block sharethis because of privacy.

It did happen to me while browsing in private mode in Firefox : https://developer.mozilla.org/en-US/Firefox/Privacy/Tracking_Protection?...