Technically, Skype is an application very different from all others. In order to fix the startup crash issue, the following must be observed:
- Make sure only one Skype.app exists on your system
- Empty the system Trash
- After downloading or updating the Skype application, a flavour (theme) must be (re)applied from Flavours.
These steps are required because Flavours modifies a file inside the Skype bundle when applying a flavour that prevents it from crashing. If after applying a flavour, Skype stills crashing, please open the Terminal application and type the command below. This will force OS X Launch Services to update its information regarding Skype.
/System/Library/Frameworks/CoreServices.framework/Versions/A/Frameworks/LaunchServices.framework/Versions/A/Support/lsregister -f /Applications/Skype.app
Note: if Skype.app is in a different location than the default /Applications folder, you need to adjust the Skype.app path above.
:: Alternative ::
As a viable alternative, you can follow the solution outlined in step 2 on the the page linked below.