On the latest version 9.0.32494. I just noticed I'm having a similar problem with my voicechat server so I think this is a Windows 8 issue. Problem is this is a fresh install of 8.1 with fresh installs of Teamviewer and the voice chat server (Ventrilo). I changed the network profile to "private" but the issue still occurred overnight.
Ventrilo is a completely different product by a different company. Maybe you have a different issue than me for TeamViewer? With your TeamViewer issue, does it work for days or weeks and then just go offline for no reason? And then never goes back online even with a reboot? And then you have to manually deleted it from the contact list and re-add the computer? If not, then you likely don't have the same issue.
As I mentioned before, I don't see how it has anything to do with Windows 8 or 8.1. I have nearly all Windows 8.1 systems and only 1 of them has this issue. And I have been using Teamviewer since LogMeIn dropped the free product about 9 months ago.
Now if your TeamViewer and Ventrilo have never worked on your specific system, that is a different issue than I am talking about here. And there are many other TeamViewer threads that cover the generic "Offline" issues.