Here's the scenario: You've got a VM that you need to use, so you TS into your host machine, start up the Hyper-V Management Tool, connect to your VM and try to use it. Suddenly, your mouse doesn't work anymore, so you try to release it using the CTRL-ALT-Left Arrow hotkey. That doesn't work. Now you can't even use the mouse on your host operating system.
If you close your TS session and restart it, you get your mouse back, but this happens each time you try to control your guest.
Some of you are probably saying "Yes - that happens to me all the time, and it's annoying!" Others may think I'm making it up, since they've never had this problem.
So, here's what's going on. There are two modes of mouse operation when we're dealing with Virtual Machines: integrated and relative, as discussed by Ben Armstrong here.
When you TS into the host machine, your mouse is running in integrated mode. When you're using a VMConnect window to control a VM, the mouse runs in relative mode (with one important caveat, which I will come to later on). When you mix integrated and relative mode, you get badness.
So what is a humble system administrator or virtualization enthusiast to do?
There are a few work-arounds: