On Saturday I started having really weird problems with my connectivity. My internal network was fine, but any external access would time out. Hubby had brought his laptop to work with him, so I couldn't troubleshoot from another machine, or verify it it was local to my machine only. Reboot the wireless router, access re-appeared. As long as I kept traffic going over the connection it was fine. As soon as the connection sat idle for a couple of minutes it would drop. I could still access my internal network, was getting name resolution on external sites, but no connectivity. Close down unneeded services, take a look at what is running (specifically newly installed stuff) and the Bonjour/mDNSResponder service was looking a bit suspicious.
I stopped the service, but no joy, even after reboot. Uninstalling LJTalk fixed the issue. I'll try it again when I have a bit more time, just wondering if anyone else noticed issues.