I'm experiencing strange problems with my Kubuntu 9.10 when doing DNS requests from various applications. The requests are extremely slow, so loading any pages in Firefox or Konqueror, doing package installations in Kpackagemanager and other apps is really painful, while for example Opera doesnt have any problems, and ping is normally fast as well for DNS pings.
I checked the proxy settings of both the used applications as well as of the general system and there are none, so to me it doesn't seem as there was something inbetween..
Does anybody have an idea on what to check for possible problem sources or how to solve this ? I'm behind a DSL home router which does the DHCP (and works well with my other computer).
Any kind of advice would be really helpful.
Edit: It seems to be some kind of IPv6 problem, as I could get it to work by disabling IPv6 explicitly in Firefox. Is there a general solution to this ?