If you are using Skype for your online activities, you might be aware of :

• screen sharing is randomly taken off and restored in the last two weeks
• skype has issues with voice connection. the known fix is to restart your computer

Here is a link, where you can check the status:
http://heartbeat.skype.com/

this is Skype owned and thus, I do not consider it entirely trustworthy.
You might want to consider also:
http://downdetector.com/status/skype

If you know more reliable reference cite, pls do share.