Can't install the software, unexplained error keeps appearing
Hi.
I'm trying to install my Creative Cloud software, but when starting the installation, it gets stuck in this stage:

After a few minutes of this, I get this:

An unexplained error, no code, nothing. I have no idea where to start, can someone solve this?
NOTES:
1. We're talking about an iMac, 5K 27', Late 2014.
2. Runs OsX El Capitan.
3. I can't "Repair Disk Permissions", because Apple have removed this option from El Capitan.