Hello I also got the same problem while trying to install forge 1.7.10.1614 today. The problem is that there is no .log file created. (Step1)When I run the "forge-1.7.10-10.13.4.1614-1.7.10-installer.jar" or "forge-1.7.10-10.13.4.1614-1.7.10-installer-win.exe". (Step2)Then I click on the "Install server" option and proceed to select and empty folder.(Step3)After that I click the "OK" button. Then the little progress window appears saying: "Downloading libraries" and under it "Downloading minecraft server version ...". And in a few seconds a pop-up window appears with a title "Error downloading" and content "Downloading minecraft server failed, invalid e-tag checksum. Try again, or manually place server jar to skip download.".
It has instructions indeed but what I personally am unable to understand is where and which server.jar file do I have to download in order to skip it's failing download.
Edit: sorry I do not know how to reduce the pictures' size.
