There aren't a lot of requirements for jPFChat to work on your site. There ARE some strong preferences for how your site is set up. The few we know must be in place are...
• A Joomla 1.5.x website. The more up to date your Joomla is... the more likely it is that you'll have very few problems.
Joomla 1.5.x includes MooTools natively. Joomla 1.0.x does not. jPFChat will most likely install and run on many Joomla 1.0.x websites. However... if MooTools is included with your Joomla 1.0.x template, or any module on your site... then there's a chance that the MooTools script being implemented on your site isn't the full MooTools library needed to run jPFChat. This will cause errors and problems.
• PHP v5.3 seems to be causing some issues. We are currently looking into this. Meanwhile, any PHP v4 or v5 before v5.3 seems to work just fine.
• MySQL 5 preferred. This is not a strict requirement, although it seems that several MySQL 4 installations are configured with database settings that seem to cause issues of one sort or another. None of the MySQL 5 based installations we've been involved with have had any database related problems at all.
• Community Builder and jPFChat seem to have some issues. The most notable are for the login process if you're using the CB login module rather than the regular Joomla login module. The currently logged in username isn't always properly picked up.
• A new Error Message we've recently seen is "Could not complete the operation due to error c00ce56e". A customer has reported that this is solved by changing the charset parameter in php.ini to "utf-8".
So... if you're experiencing any other issues... let us know some details. We would most likely want to see the problem symptoms for ourselves.