Seeking Recomendations: chat application with whiteboard

[Dave M G]

Ubuntu Users,

I've just been searching Google without much success. I'm looking for a 
chat application that has a whiteboard feature. Audio chat would be good 
too. Video is un-needed.

The person I am intending to conference with also runs Ubuntu, so cross 
platform is not needed. But they are more comfortable on Windows, so 
cross platform, perhaps Java, would be good.

And, ideally free and open source.

Does such an application exist? I can't find anything obvious either 
with Google, or within Synaptic. I hope that's simply because I 
overlooked something obvious.

Any suggestions would be most welcome.

Thank you.

--
Dave M G