Web Share from Ubuntu host gives black screen - from all clients.

Steps to reproduce:

Run YuuGuu on Ubuntu 9.04 64-bit (installed from provided .deb build.2722).
Start Web Share.
Click Show.

Now on any other client connect to http://www.yuuguu.com/share and input the appropriate PIN and name. The session looks like it's loading - the viewer portion of the browser goes black, says connecting...connected and then runs to 100% but then stays black, and no image of the desktop ever shows up. Changing the mode from Full Colour to Fastest on the Ubuntu host makes no difference, neither does requesting/granting control of the screen.

This behaviour affects ALL clients I've tried it on (XP + IE8, XP + Firefox 3.5, Ubuntu 9.04 + Firefox 3, OSX Leopard + Safari) when trying to connect to this Ubuntu host session.

Viewing a Windows-hosted webshare on these platforms works fine.

Nothing of any use is logged in the debug log of the Ubuntu host. This is all that is ever logged (log level is "ALL"):

---
29-Jul-2009 12:26:38 com.yuuguu.client.update.UpdateManager isInstalledReleaseValid
FINE: Checking installed release for validity
---

Can anyone help? This functionality would be VERY useful for me to quickly screen-share with non-technical people without having to tell them to do anything complicated. I would just use Skype but on Linux it doesn't provide screen-sharing like the OSX and Windows clients do...