I didn't see this in the other comments but I thought I would add this answer from Lenovo:
https://support.lenovo.com/au/en/documents/ht079944
I just found it today so I haven't tried it yet. Usually I fix the issue by powering down, and then turning on again, and I can do what I need to. Also I have upgraded to Windows 10 - still same issue so I plan to try the lenovo suggestion. Using ThinkPad 8