@doktornotor:
The problem probably is that you switched the error messages locale to NL but the state of Squid localization sucks goats nuts, to put it mildly. Leave that at English, unless you'd like to finish the translations and submit them upstream.
Hello doktor,
Thanks! Nothing to worry about then. Can you tell me where I can change this? Logging settings for squid (access.log) is turned off.