Version: 4.2.23 both client and server, both Windows 8.1 machines.
I have this problem as well. It worked initially but somewhere along the way (and there were Windows updates in that interim period) I have lost the mouse pointer. The pointer still works, it is just invisible – for instance if I right click on the desktop I get the context menu. None of the things listed here seem to make a difference, I have also tried both on and off the “Show remote cursor” option in NoMachine. This only happens to a Windows target machine; my Linux machine acting as a server still works fine and shows the pointer.
Additionally the mouse mapping within the displayed window appears non linear, regardless of acceleration settings. That is to say if I place the mouse cursor immediately outside the NoMachine window, then move the cursor in, the (now invisible) cursor is not in the expected location, but shifted.
Given what Olloff and I both have seen I imagine this is connected to a Windows update in some way, particularly since mine worked before.