Blank page when clicking on user name in user list

Hi,

I use CB 1.9.1 and Joomla 2.5.17. I have the web site for more than 2 years and everything was working fine. Somehow the mandatory menu User Profile has stopped working and with it the possibility to see users profile when clicking on some user name in the user list.
When I click on the menu for the user lists and click on the name of some of the users I get blank page and only message This user has no current connections.
When I am logged in I get the message There is no established connection between you and X.

I have settings done as here www.joomlapolis.com/support/tutorials/96-configuration/18231-enabling-cb-connections
User lists are public, also the User profile menu. The user profile menu is part of the User menu.

You can test here:
tortijada.mk/index.php/mk/slatkari-slatkarnici-mk
tortijada.mk/index.php/mk/profil-slatkar/userprofile/KanelA


Please help me to solve this problem!

I have just decided to go through CB plugins in the Plugin manager and have noticed that when clicking on Community Builder System plugin it gives the error message 500 - An error has occurred.
The file communitybuilder.xml could not be found.

Can this be causing the problem and if is how I can fix this???

Thank you