If you're using 1.1, please upgrade to CB 1.2 stable, which has remedied all known bugs. If you're using 1.2, you're posting in wrong forum and need to enable the Joomla Legacy Plugin or find which extension or CB Plugin you're using that is not Joomla 1.5 compatible.
Thank you very much for your opinion. I had one plugin cb_profilebook. I read your message and I uninstall it, and the community builder works very well.without problems.
I just wanted to add a sidenote that the new CB 1.2 version of ProfileBook also allows a Blog tab and Wall tab that's greatly enhanced. This is currently available to documentation subscribers.