There are some weird and obscure ways to program things. Such ways can lead to what we have currently in Skype under Windows 8/8.1:
If you have not IE as default browser, your Skype eats up CPU and lags as hell.
And make IE as your default browser is NOT a solution — since we don’t cooperate with bad guys and dirty methods 😉
Actually there is simpler workaround:
Turn off all systray event notices
Turn off «Display avatar in contact list»
That’s it! Maybe you’ll be forced to read all messages and restart Skype before lags stops, but at least you have now way.