I faced problem by downloading (deb file) and installing skype from skype.com. May be it occurs for version mismatch. Skype don’t provide skype for all version of ubuntu. Skype authority isn’t much active in development on linux environment. I am using Ubnutu 13.04 and there are no specific skype version for this linux destro. The main problem was I wasn’t seeing any skype notification icon at top right. Somebody said Skype is no more in canonical repository but it is still there, I am not getting any problem by installing from here. Open Terminal and add the repository, update list and install skype.
sudo add-apt-repository "deb http://archive.canonical.com/$(lsb_release -sc) partner"
sudo apt-get update
sudo apt-get install skype