After returning from vacation I was confronted with a really strange problem on my laptop. Firefox wasn’t any more able to load pages from certain domains. After a reboot it worked, but sooner or later it stopped working.
At first I suspected a network problem, but my Windows PC was still able to load those pages.
I played around with the settings in /etc/nsswitch.conf. This made nslookup work correctly, but Firefox and wget etc still wouldn’t work. Very strange – you’d think that they would resolve a name in the same way as nslookup or host would do.
Eventually I found a solution: Disabling the DNS proxy in the Samba configuration file (setting ‘dns proxy = no‘ in /etc/samba/smb.conf) did the trick.