That’s not a known or likely conflict, and could very well be another plugin (possibly your theme) misbehaving under certain conditions. Have you tried enabling only AddToAny and Disqus?
Disqus has a doc on a number of possible causes: http://help.disqus.com/customer/portal/articles/960360
The Disqus plugin also handily provides debug information at the bottom of Comments > Disqus. Feel free to post and info here.
I have tested it out. When I disabled addtoany, disqus will auto sync, when I enable it, disqus will not auto sync
URL: (my website url)PHP Version: 5.4.24Version: 3.8.1Active Theme: Point 1.0.6URLOpen Method: curl
Plugin Version: 2.74
Settings:
dsq_is_installed: 1
_disqus_sync_lock:
_disqus_sync_post_ids:
disqus_active:
disqus_forum_url: dkk
disqus_api_key: (secret)
disqus_user_api_key: (secret)
disqus_replace: all
disqus_cc_fix:
disqus_partner_key:
disqus_public_key:
disqus_secret_key:
disqus_sso_button:
disqus_sso_icon:
disqus_manual_sync:
disqus_disable_ssr:
disqus_last_comment_id: 1236633096
disqus_version:
Plugins:
Akismet 2.5.9 (active)
Better WP Security 3.6.3 (active)
Blogger Importer 0.6 (active)
Blogger To WordPress 2.2.3 (active)
Disqus Comment System 2.74 (active)
Redirection 2.3.4 (active)
Share Buttons by AddToAny 1.2.8.1 (active)
W3 Total Cache 0.9.3 (active)
WordPress SEO 1.4.24 (active)
WP-Optimize 1.6.1 (active)
Re-reading your first post, this is not an AddToAny plugin issue. If your Disqus auto-syncing worked with version 1.2.8.0 of AddToAny, then AddToAny isn’t your issue here because version 1.2.8.1 was a very minor plugin release.
AddToAny is working great with Disqus on many other WordPress sites right now, so marking this topic as resolved, but you should post a new topic in the Disqus plugin support forum after troubleshooting some more.
Additional thoughts for troubleshooting before you post the new topic:
Your site might be erroring upon that auto-sync, and the issue could be caused by any additional plugins loading. You should log and read any Disqus errors/notices that occur upon that auto sync. WP_DEBUG_LOG might help:
http://codex.wordpress.org/Debugging_in_WordPress#WP_DEBUG_LOG
Disqus sync can conflict with caching plguins such W3 Total Cache:
http://wordpress.org/support/topic/plugin-w3-total-cache-w3tc-breaking-disqus-comment-syncs?replies=6
You’re not alone in having Disqus auto-sync issues:
http://wordpress.org/support/topic/comment-sync-not-working-manual-sync-works-fine?replies=1
Good luck!