I checked it. In fact, the change from "vocalfreaks.pl" to "www.vocalfreaks.pl" helps.
The problem is that some people come from the first address, the other from another, and it will be a problem at all to explain to them what's going on.
I have one little clue.
The problem occurs only when I enter the board, never, when chat is working.
After that I must refresh site (sometimes many times) until the plugin will start working.
Of course, I'll still be trying to find the problem.
When I installed your plugin on my board I have control panel issue.
When I click on User Settings I simply got a message like that "That action could not be completed. Please try again, and if this occurs again please contact the system administrator and tell them how you got this message."...