If you're using the CakePHP framework and are having a problem with output buffering, this quick tip on the ThinkingPHP blog might work for you.
Output buffering is a useful way to accomblish things in php like gzipping all html output and such. A while ago I wrote about it on this blog (see "A miracle called gzip") as well.
The reason I write about it again is, that I have discovered a little issue with it in CakePHP.
He notes that if you just use the ob_start with the gzip handler, debug issues arise. The soultion he's come up with, though, isn't quite as simple, but gets the job done in about ten lines and is easy to drop in anywhere.