Make sure you allocate enough memory or you could have weirdness such as blank pages. Try a configuration with 128M cache and increase as needed. Please note that this value is for the whole server, thus, if you have many Tiki instances or other PHP apps, you should expect to increase accordingly.
Check the eAccelerator section in tiki-phpinfo.php
Memory Size 134,217,664 Bytes Memory Available 56 Bytes Memory Allocated 134,217,608 Bytes