I found the solution to the "IRC Chat Java Client" not working while working on another similar problem with Web SDR apps not working. It seems that Java has given up trying to deal with security problems and in the latest Java versions you have to put the URL in the Java "Site Exception List" by hand.
- Run Java Control Panel ("Configure Java" via Windows Start)
- Go to Security Tab and pick "Edit Site List"
- Add
http://www.starchat.net (needs the http://)
Then try again and answer OK to all the messages...