When attempting to either install, update, or upgrade to Camtasia Studio 8.1.1 you may run into a message stating "Fatal Error" and then it will roll the installation back, and closing out of the installation.
If for some reason you are unable to update you can de-select the library option as shown below as a workaround.
Once the option is deselected, continue through the installation process and the application should install as expected.
As the install method above does not include the Camtasia Studio default Library assets you will need to manually install them. You can download the Camtasia Studio 8 default Library assets from the following link: http://www.screencast.com/t/ZFoNrfOnm (click on the "Download this media" link).
After downloading the above file, open Camtasia Studio 8 and go to the Library. Once there, right click in the Library and choose to Import Zipped Library.
In the popup window, click on the small folder icon to Browse for your downloaded file.
Once selected click "OK" and the default Library will be imported (this process may take a few minutes).