Anonymous - 2012-02-02

I have a very weird issue. I have moved out my phpBB forum with chat and database to another hosting provider.
I have changed in the config.php file the new username and password for my forum database. Everything works fine, but I can not log in to chat.
After I log in to forum and I press chat button, I need to re-login again in the chat. After I login to the chat, in 1 second the chat logged me out.
I have deleted all ajax_chat* database tables and I reinstalled again, but still without any success.
Can somebody help me with this issue, please?
Thank you very much!