The TYPO3 caching framework in TYPO3 4.5.0 runs into troubles when using memcached backend on Debian Squeeze. It seems that Squeeze ships a broken php5-memcache package, which does not fit the API of memcached 1.4.4. Since Squeeze is already released, there will be no fix in the official stable repository. But I provide a fixed package for download.
After a dist-upgrade from Gutsy to Hardy on our webserver, TYPO3 was suddenly broken. The reason is a bug in PHP 5.2.4. There is a workaround for TYPO3, but unfortunately the patch is still pending in the core list.