I'm suspicious that this problem may have something to do with Kunena - it seems like this happens after replying to a post in the forum on my site. In CB user management, clicking on a user OR simply entering a search term in the CB user list results in a blank page, even with ALL error reporting options at maximum. CB reports no database problems, and users have been synchronised.
versions:
Joomla 1.5.14
CB 1.4
Kunena Forum 1.5.6
PHP Version 5.2.6
Apache/2.2.9 (Fedora)
