Paste doesn't work in uVision 4.72.10.0 on Win 7 & 8 probably solved. I had the same problem both in windows 7 and windows 8 on 64 bit machines and I had recently installed the Webroot internet security. Having tried almost anything, unistalled keil reinstalled it etc, I found that when I disabled the internet security shield the "paste" function had recovered. I downloaded both 5.12 version and 4.72 version of keil and after that copy and paste works on both versions. So to anyone who is interested, any other software that may be running live shields or blocking anything real time, disabling it may solve your problems.
HUGE thanks Panagiotis Georgiou. I had the same problem with uVision 5.13 on Win8.1 x64 and this solved it immediately.
It was Webroot just for documentation sake.