I've got an interesting issue.
I'm running Kubuntu 16.04 LTS with KDE Plasma 5.5.5 and Qt 5.5.1 on an HP Elitebook 1040G3. Whenever I put my laptop to sleep by either locking the screen, shutting the lid, or simply leaving it idle, the mouse cursor completely freezes when I wake the computer. Interestingly, it continues to work for a few seconds immediately after wakeup before freezing.
By "frozen", I mean that I can neither move the cursor nor click on anything it happens to be hovering over when it freezes. It is important to note that I still have full control of the computer with the keyboard as if nothing went wrong and can open terminals, browse the internet, etc. just fine.
I can fix the problem by simply logging out and back in. However, this, of course, takes some time, and its quite inconvenient to have to log out every time I'll be away from my computer for more than a minute or two.
I've attempted to remedy the issue by reinstalling xorg-input drivers, but I'm either not reinstalling the right ones or the problem exists elsewhere.
If there's anyone out there that is having this issue... I found a solution, but you might not like it.
Annoyed with having to completely log out every time I open my laptop lid, I completely reinstalled my operating system. This time, instead of using Kubuntu, I went with KDE Neon 5.10. I no longer have the issue, and the operating system is more or less the same with some extra features!