YANGMEYER Sorry for only replying now. You are right, there is a critical bug in version 0.4 of the Rendezyou client. We messed up this release, and we're profoundly sorry to everybody who gave Rendezyou a try and was disappointed! We humbly ask everyone to give us, and our little but useful app, a second chance.
This bug will be fixed in version 0.5, scheduled for release this Sunday, Jan 10. In the meantime, users of version 0.4 can *work around the bug* by manually creating the folder "~/Library/Application Support/Rendezyou". You should then be able to drag iCal events into the app.
Try it out – invite some friends to go to the cinema (which film? when? where?) and see which suggestion makes most sense. Enjoy! :-)
(Version 0.4)