My skype stopped working on my powerbook g4 the other day but I found this post elsewhere on the internet and it solved my problem. I'll paste it here if anyone else has the same issue, and sorry if this info is already here somewhere else that I didn't see....
Try taking the following steps:
1. Quit Skype
2. Go to Applications Folder in Finder and Right Click on the Skype icon
3. Select “Show Package Contents”
4. Click on Info.plist
5. Scroll Down until you locate Locate these 3 lines:
CFBundleVersion
6.15.0.335
Replace with:
CFBundleVersion
7.36.0.507
6. Then go to File and click on Save, or press Command+S
7. Re-open Skype
8. If that doesn’t work, then uninstall Skype as instructed by the creator of this thread and then Download
from a safe website Skype Version 6.15 for Mac.
9. Install Skype by double clicking on the downloaded file and dragging the Skype icon to the
applications folder and Repeat steps 1-7 in this comment.
10. Then go to Applications, Open Skype and Log In.
Hope that helps