Hi Gary, thanks for being understanding.
Unfortunately, I have further bad news for you. The reason why I asked for the serial number and mentioned that it would depend on your Mac model is the fact that while OS X 10.5 will support versions of Skype up to 6.3, this is limited to Intel based Macs only and not your Power PC G4 model.
As you are using a G4, 18.104.22.1686 is still the newest release to support that architecture.
Outside of buying a newer Mac, if there is someone you frequently Skype with then you should ask them to downgrade to a slightly older version if possible.
Here is a listing of the versions that 2.8 is NOT compatible with:
Skype 6.2 for Mac and above
Skype 6.2 for Windows desktop and above
Skype 4.8 for iOS and above
Skype for Android
Skype for Windows Phone
Sorry for the bad news again but I will assist you in any way I can.
I can be reached directly via the following page. If you also request me by name in the question you submit that will usually hold the question for me a bit longer, if I am away from the computer:http://www.justanswer.com/computer/expert-macdruid/