Since upgrading to 8.1 on my Surface Pro the following VPN applications seemed to stop working:

Cisco VPN Client

Shrewsoft Access Manager

As well as a web-based client we use through f5 networks.

They all give similar errors, which point to not being able to open up a virtual adapter, or the network generally being unavailable.   I tried the usual registry edits for Cisco VPN, I tried different combinations of running as administrator, windows 7 compatibility, windows 8 compatibility, Vista, etc.  Nothing seems to fix this issue.  There must be something fundamentally different in how 8.1 handles virtual network adapters that is breaking all of these clients.

Any workarounds found?

I've wasted a tremendous amount of time trying to get both Shrewsoft and Cisco VPN clients working on my Surface Pro with Windows 8.1 Preview installed. I have given up the fight and will be performing a system recovery to get back to Windows 8 Pro.

What did you end up doing?

Right now I'm hoping someone finds a fix or the next build/update has a fix.  My surface pro is the system I take around the office to meetings so it's not such a big deal while I'm at work.  However, I do take it to offsite vendor meetings too which is when I noticed VPN was broken.

When I work from home I have a desktop gaming PC that I want to update to 8.1, but can't, because of this issue.  

Here's to hoping for someone to find a fix/workaround/hack.

I've been able to get Cisco AnyConnect working just fine on 8.1.  I can't even get Shrew installed, it just hangs at one point and I had to reboot to kill it.

Citrix appears to be working OK as well.

I haven't tried the AT&T VPN yet.