Why would one of my hosting servers be connecting to ports on a visitors machine?

> The firewall has blocked Internet access to your computer (TCP Port 7869)
> from www.xxxxx.xxx ( (TCP Port 35261) [TCP
> Flags: S]. Time: 15/09/2002 19:00:38

I've got 4 php driven sites which for some reason have started making connections to the visitors machines. There don't appear to be any sessions or cookies used.

The sites have just recently been moved to a new server so obviously something on the new server isn't quite right but I'm not sure whether to be looking at the global apache settings, php settings or something specific to each site?