While testing seaside when loading the pages locally in firefox I had a long delay. After some digging,
it turns out that the slowness is caused by an IPv6 issue with DNS and can easily be resolved by turning IPv6 support off in Firefox while doing localhost testing. To make the change, type about:config in the address bar, locate the network.dns.disableIPv6 setting and double-click on it to set it to true. This does the trick for the Firefox localhost issue on Vista and everything is running fast again.
as it turns out other people had the same issues but not in relation with seaside, therefore I found it in google only after having discovered the solution by myself.
I am hopping that blogging it under seaside/squeak will help someone save some time.