I've been fighting that problem (with help from Dave) for about a month. On one computer, the solution was to download and install xchat (www.xchat.org). There is a thread on SRP with some help installing and configuring xchat (http://straightrazorpalace.com/gener...-srp-chat.html). If that doesn't work, as it didn't on my other computer. The problem is probably some kind of firewall or security setting. In my case, my new laptop came with something called the "infineon security platform" that needs to be initalized and I don't want to deal with it right now.
If you haven't changed anything on your computer, chances are that Windows Update has changed something in your firewall settings. I'm not computer savy enough to tell you what, but that's where I would start to look.