Uploaded the files for a fresh install, and this is what I get:

(I reseted my license URL before downloading Beta 7)

Server meets the requirements, I have a 3.4.7 install and ips4.php test for the suite yields everything green.

Found some error logs...

[Mon Feb 09 22:03:54 2015] [warn] [client 37.14.205.94] mod_fcgid: stderr: PHP Fatal error:  Uncaught exception 'ErrorException' with message 'Unknown: open(/var/lib/php/session/sess_nldd5v17513ni6krh7ecgcv950, O_RDWR) failed: Permission denied (13)' in Unknown:0, referer: http://www.unrealspain.com/admin/install/

Any ideas on how to fix this? I suppose it's something in my server.

That's a server error - for some reason your server is not letting PHP sessions work.

Permission error, so check permissions on this folder:

/var/lib/php/session/

Well changed the PHP handler from FastCGI to Apache module and it seems to be working now.

Errr, I finally figured this out, and I thought that I could drop the solution in here in case it's useful for somebody.

I'm using Plesk 12 in my CentOS server. Running php as cgi, it uses the ftp user permissions, but /var/lib/php/session is owned by root:apache, thus the ftp user doesn't have permission there.

I didn't want to give that thing 777 permissions, so I configured a custom php session folder in the vhost and set the ftp user as its owner, with 0700 permissions.

Now everything works like a charm using FastCGI.