It's not an RSLinx software issue, but rather the "Get Plus" downloader utility that Rockwell Automation uses. Depending on the OS and browser you are using it can (I think) be an ActiveX or a Java applet.
Try using a different browser, and watch carefully for any security popups or status bars.
Just an unrelated issue But might help
I had an issue with the kinco screen software and win 8.1
Changing the compatibility mode back to win 8.0 solved it.
Try setting the mode to win 7 or XP