Safari 7 Mavericks not loading Facebook

Since the update to OSX Mavericks and Safari 7, Facebook and some other random pages were not working properly. Sometimes FB did not load at all, sometimes images where missing etc. After googling and asking others it seemed like I am the only one that had the problem. In other browsers the pages work as expected, so it was a strange problem, and I was really happy to find out the cause: in the network preferences->advanced->tcp/ip I set the ipv6 configuration to “Only link-local” (translated from german, maybe called different, it is the last option), and everything was fast as usual. So it seems there is a problem with ipv6 handling anywhere.. So because not many people complained about this issue, I checked my cisco WRT610n router and found out that it has a messed up ipv6 handling which caused the whole thing after the OSX update.