I downloaded version 7.1.4 RTM, but when I run the installation program LINQPadSetup.exe, the installation still shows version 7.0.6
on the title bar.
Try again - I suspect your browser is caching an old version.
Note that LINQPad is self-updating, and 7.1.4 is now RTM. So in any case it will automatically update to that.