Hi,
Cleared cache and restarted app but it does not solve the problem. In event log after those actions i found only one error message:
[SchedulingExecutor.ExecuteTask]: Cannot load the provider class 'CMS.WebAnalytics.HitLogProcessor' from the assembly 'CMS.WebAnalytics'
I have not done any changes to the chat module or site (clear installation). Only what i did was that i created first site without any template and then removed it completely, after that the second one was created using social network template.