Can you update your site backend and FTP access at http://stackideas.com/dashboard/site so we can better have a check?

Done...

Hey,

I have checked your site and the problem seems to be the way Simcontests is adding the activity stream and generating the activity stream, http://take.ms/ADbjN . This issue is not related to EasySocial.

I have added a temporary fix for Simcontests app, http://take.ms/9vdCr and it should work fine now. However, I strongly suggest that you report this issue to the respective developer.