Typing 'http://:' into a Skype Message Trashes the Installation Beyond Repair
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It seems like the issue is that the Skype installation maintains a chat history. If this poison string is in your chat history, something crashes the client (presumably a procedure intended to linkify URLs in chat).
You can delete your chat history, but it is synced from the server on startup, at which point the client crashes again. That's why your only option is to downgrade to a version without the bug.