Here is a quick workaround for the "skype opening only once in Leopard" problem.

The problem: As a security measure leopard check's each installed application to see that it has not altered (even by just 1 byte) since last launch. Skype modifies it's self after the first launch, hence it will launch only once under Leopard.

Workaround: After each launch of skype, remove it from the application's folder to the Trash. Reinstall skype from the dmg or image. The firewall will again ask permission for incoming permissions. Click open and skype works as usual.

Look's like skype have some coding to do.

Or, launch skype on 10.4, then copy Skype.app to a 10.5 install, like I did.

Another option is to turn off the firewall

i never had any problems at all.... strange.

edit: oh i see you mean you can only launch it once per start-up. I guess just restart. its easier than re-installing it.