Watin - Firefox error

From time to time when I run my Watin tests, I get this error:

WatiN.Core.Native.Mozilla.FireFoxException: Unable to connect to jssh server, please make sure you have correctly installed the jssh.xpi plugin ---> System.Net.Sockets.SocketException: No connection could be made because the target machine actively refused it 127.0.0.1:9997

I can confirm that I've got JSSH plugin correctly installed, and also the strange thing is that this is not something that happens all the time.

Installed versions of Firfox and JSSh plugin:

Firefox: 3.6.13

JSSh : 0.9

Appreciate if someone 开发者_JS百科could shed some light on this as this is causing me lots of headaches.

Thanks.