Support indicator-applet
The new release of Ubuntu - 9.04, intruduced new, actionless notifications. Gajim did not check if the notification deamon actually supported actions, so it has been patched.
Since Gajim has been fixed to utilize the new actionless notifications of Ubuntu one cannot just click on the notification bubble when a message is received to open it up. One needs to click the notification area icon to open up the roster window, find the person who sent the messege on the roster and click that contact to read the message.
This situation could be prevented by implementing indicator-applet support. https://launchpad.net/indicator-applet
There is documentation available in the tarball.