I have a Java chat-like application using Comet using Grizzly Comet, which works in Chrome but not in Firefox (latest versions of both). It uses the HTTP streaming method, sending Javascript snippets down to a hidden iframe ("forever frame") to be executed. On Firefox, no chat messages are displayed initially, until a few messages have been sent by a Chrome user - then it springs to life and works.
No proxy is in use, so it's not a proxy issue.
What could be the problem?