Falls es eine andere Antwort ist als das, was ich gerade gefunden habe, schreibs ruhig noch rein; falls der Fehelr noch da ist.
Ich fand folgendes über den Link im Browser selbst; die anderen gelisteten Möglichkeiten waren es nicht.
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IPv6
Internet Protocol version 6 (IPv6) can cause connection problems on some Internet connections. It is most likely a problem with your router, firewall, or ISP(Internet Service Provider), but it if affects Firefox because Firefox uses IPv6 by default. You can disable IPv6 to see if this solves your connection issues:
1. In the Location bar, type about:config and press EnterReturn.
* The about:config "This might void your warranty!" warning page may appear. Click I'll be careful, I promise!, to continue to the about:config page.
2. In the displayed list, type network.dns.disableIPv6 in the Filter textbox.
3. Find the entry for network.dns.disableIPv6.
4. If the value is false, double-click on it, to change the value to true.
* If the value is already true, IPv6 is already disabled, so it isn't causing your problem.
5. Close Firefox, start it again, and try to reach a website.
If disabling IPv6 solves the problem, report the issue to your router/firewall manufacturer or ISP. If disabling IPv6 does not solve the problem, re-enable IPv6 by setting the preference back to false, otherwise you will not be able to connect to IPv6 websites.
