Working OK for me using KB, RMB menu & scripted copy/paste/rename functions on w7x64, MC 5.9 2058.
However I think I have had this behavior in the past but not with enough consistency to say 100% it was MC & not a sticky mouse button etc.
I noticed it when I'd copied a file & then tried to paste into a new folder & nothing happened - I was using keys not MCs button menu.
Happened a few times so maybe something else is going on?
I have some misgivings about the nvidia driver which seems to have introduced some sort of random erratic response to the system since #360.xx, again not consistent but I've just done a fresh install of W7 with very few unknown quantities, so it should be 100%....
(Also ran Memtest86 w/out errors.)