I'm having the exact same problem: first time I've seen it happen when installing a new FARR. "Failed to save license key information; check to see if you have permission to write to the application directory." it says. I have full write access to my hard drive!
While I'm at it, may I request that you put some more "smarts" into the installation process? I tried to install FARR v1.09.04 while a previous version was still running. Normally, most installers would detect this and automatically close down the current TSR. But FARR just gave this cryptic "cannot delete file" message. Took me a couple of tries before I realized I had to manually close down the old FARR tray app first!
Even stranger: when the first installation failed, I thought I had to manually uninstall the old version first. But when I went to the Add/Remove Control Panel applet, the entry for FARR was gone! So the aborted install seemed to remove the entry first.
Hope this helps.