Skype 4.3 for Linux fixes group chats
Skype has been updated to 4.3 on Linux. This fixes group chat issues with non-linux clients.
If you have previously installed skype via ubuntu packages, you need to remove those fist via
sudo apt-get remove skype skype-bin
Note
Try to install the 32 bit version. In serveral cases this was the way that worked out.
Grab the installer here: