I upgraded to 300 MB of RAM recently. The continous swapping almost stopped and the constant reloading was also reduced.
Furthermore, I don\'t get this error anymore. Instead, PS simply crashes with \"illegal exception\" ore somesuch everytime.
Therefore, I believe that the mentioned error is an indirect result of the continous swapping / realoading that uses up the CPU power due to hdd activity and / or resource locks. Therefore, the client doesn\'t send a message to the server in time (keepalive). Because of this, the server thinks the client has crashed (as it\'ll do anyway, as the playability duration didn\'t exactly increase) and closes the connection. When the client finally sends it\'s message to the server, it gets the response that the server dropped the connection, which is exactly the case, due to (percieved by the server) inactivity.
The inevitable crash might be a result of my particular hardware or O\"S\", though.