This was reported as being a bug in the version of the software you currently use. The official fix posted on various forums indicates that a fresh installation of Skype is mandatory.
Access the official website and download the newly released version of Skype, then visit the Macam website to download the compatible drivers.
For Skype it is absolutely necessary to have Mac OS X 10.5.8 or higher. It doesn't work for versions prior to 10.5.8 release.