Macintosh HD and Finder are both known for over-reporting the amount of free disk space due to the local Time Machine backup. These backup files actually don't get counted against your hard drive space, increasing the amount of "free" space that you're seeing.
To get an accurate measure of remaining free space, try running a Mac OS X System Report and see what that reports back with. To do this, you'll just need to run through the following steps:
Click on the Apple in the upper-left corner of your screen
Select the "About this Mac" option
Click "System Report"
Navigate to the Hardware section
Select the Storage option
Look for the Hard Drive that you are Using and look for the amount of free space remaining
If this number is still well above the 80GB that the launcher needs to install, please please submit a ticket to our support team and be sure to include a copy of your System Report .spx file. This can be done the following way: