Gregor, please update the phex gwebcache to a more recent version of Beacon Cache II.
Right now you're using v. 0.2.2.1 when v. 0.7.3.1 is the latest.

With the newer version, there are many improvements and additions to the settings.
A big thing I noticed: The very outdated version you're using seems to be connecting to remote caches to test, despite being set to 0 urls to be stored. This issue was fixed in a more recent version.

Also, with the new version comes with an updater script, so that browsing to it will check and auto-update your cache. It will only work though if the installer has first been run, and you've kept update.php and keep_for_updates.php (created by the installer) in the same directory as gwc.php.