Did you reboot the PC before trying the install?

Was there a previous version installed?

Dear Diabolicus!

From your logs seems you have previus version installed and it cannot be deleted:

Error 0x91 Removing folder: C:\Documents and Settings\All Users\Application Data\Symantec\Symantec Endpoint Protection\12.1.2015.2015.105\Data\Cached Installs\Program Files\Symantec\Name\Version

If it not an upgrade you should use competitive uninstall settings or you should manually delete a sep client from the server and after try to deploy again, if it not going try to export and install a sep package.

Some ideas for the removeing:

http://www.symantec.com/business/support/index?page=content&id=TECH184988&profileURL=https%3A%2F%2Fsymaccount-profile.symantec.com%2FSSO%2Findex.jsp%3FssoID%3D13599840837699ZKXIjkZu4hTuf101t1D38RGKmV48dgZYdG21#ClientUninstall

Was there any previous sep version installed on that server?

No previous SEP Installed, but McAfee present.

I'll try with Uninstall feature embedded in the package.

I've performed NO reboot because we can't reboot that machine (I know it's some sort of "DUTY" but not possible at the moment... other 80 servers ok, I'll try with this).

Your install Log shows

"ScriptGen: ShowServiceProgress() script execution failed.

ScriptGen: ShowServiceProgress() reset script failure event.
ScriptGen: ShowServiceProgress() is returning an error (so close to the end!)"

So recommend following:

http://www.symantec.com/business/support/index?pag...