I've never had this problem on other versions of FSX but since I have recently changed over to Windows 10, from Windows 7, I tend to blame the OS for this and not the Steam version of Fsx.
What happens is that occasionally and seemingly at random, although probably more with PMDG products (video intensive?) the mouse cursor totally vanishes and pressing or moving the mouse produces a long series of beeps. I close FSX using the keyboard but the problem remains until I reboot the computer. I should mention that I play FSX in Nvidia Surround on three monitors.
I have had mouse problems outside of Fsx since Windows 10 even though I think I have the correct drivers. I have also uninstalled all USB hubs from Device Manager and they were reinstalled after a bootup. This did not fix the mouse beeping problem which seems to occur only in Fsx. I welcome any suggestions. Thanks
Charles