Funny one I ran into recently, where your mouse cursor will just go crazy when using a office application , constantly flashing or blinking as if its trying to load a program. Here are the Fixes
1. Check your Default Printer
have you installed a new printer recently or updated drivers, This is known to cause the blinking mouse cursor issue in Microsoft Word. Change your default printer to see if you see any changes. Or uninstall recently installed printers and reinstall using most recent drivers.
2. Antivirus Software
Disable your anti virus software to see if that fixes the issue. Especially a piece of software that performs in the background virus scanning.
3. Disable your Word Addins and Macro's
4. Check your task manager for processes with High memory and or CPU usage
5. Try different usb port, having a dodgy usb port thats not supplying enough power can cause this issue in some cases.
6. New Mouse Time