Refer to the stickies in the long list of Bugs in the CB 1.1 -> Bugs section. CB 1.1 was made to run on J1.0, so there are a lot of issues when running on 1.5. Also, most developers won't support PHP 4 anymore. You may want to upgrade to PHP 5 for maximum performance and security.
If you're determined though, the stickies I referred to contain fixes, as well as the FAQ link in my signature.