Sounds like there is a file you're not getting. Never do a removal manually. It's so time consuming and a pain. There's a very easy and fast way to do this, safely, properly.
Get the free "Final Cut Remover" app from Digital Rebellion (dot com), use this to remove FCP X.
Reboot the Mac.
Download from scratch.
If you're not seeing FCP X in your app folder, run Disk Utility to Repair all drives.
If that doesn't help, try running Disk Warrior from Altsoft to repair the directories on all drives.
Hi, thanks for feedback. I tried out you first two suggestions, and I think it didn´t work in my case. Seemed like I got all the files removed with Final Cut Remover though. Then I tried an upgrade of my OS to Mountain Lion 10.8.2 to see if that helped, and it actually did. Final Cut installed perfectly after upgrading to Mountain Lion, if removing with Final Cut Remover did part of the job I don´t know...maybe.
Then I didn´t try the last suggestion with the Disk Warrior cause upgrading OS seemed cheaper than buying Disk Warrior.
Thanks anyway for your help!