I've started a very basic chat client based on the sample client delivered with the XIFF2 package, the XIFFExample.fla.
The client works perfectly when ran as a standalone app in the flash player but seems to have troubles running as embedded in a web page.

I'va attached the fla & php file I am using. The main differences between the original fla and my version are :
1. I Removed the Room support (since I need a 1-to-1 chat)
2. Added a debug function that display misc data in Red
3. At the line 160, I've hardcoded a nickname "debbie" to chat with. It can be changed of course.
4. In the php file, I pass my nickname on the server, the server and the domain as flashvars.

I have a feeling the problem lies in point 4 ... anyway, thanks for helping me.