I’ve noticed this during the last couple of updates of the unreal launcher, including the one this morning that (I think) shut down the marketplace. For a period of about 30 to 60 seconds I will find my cursor locked in position. I can alt-tab, control-alt-del and type fine, assuming the focus is on a text box. Clicking appears to work, assuming the cursor is over something click-able. But the cursor won’t move. Once the update completes, the cursor is free and I can move it anywhere on the screen.
For reference, my computer is an MSI GT70 2 PC Dominator laptop with a Synaptics trackpage running Windows 8.1
Update: Just started the launcher and received the new update that added the learn tab and updated the market. I didn’t noticed any cursor lock this time. Could it be when the Launcher is running and a change is pushed to the Launcher that the cursor is locked at some point during the update process. Is there a way to test this?