Hello,

Why am I being requested to enter a username and password to complete my download?

It requests authentication with username and password for site wcp.11df.edgecastcdn.net

Why is that and how am I supposed to know that password?

Thank you!

What download? You mean when downloading the game you have bought?

Edit:
You should register in the site to be able to buy any game.

Yes. I registered in gog.com, bought Icewind Dale game and at the end of the download progress, at 99%, the download window prompts me for a username and password for site wcp.11df.edgecastcdn.net.

Shouldn't the download finish as normal?

Restart the computer, that shouldn't happen.

Don't enter any information! This looks to me like a phishing attempt. Do you have any antivirus?

Are you using a "download accelerator" like Getright, free download accelerator, or any similar tools ? or are you using a proxy or some ISP that might change your IP address in the middle of the download ?

I was using Download Accelerator Plus, I never thought I was going to be prompted for a user and pass, never happened before.

Anyways, I know it may be that then, I will use the GOG Downloader.

Thank you all!

GOG's download links expire after a short time. This means that if a download accelerator tries to make new connections to the same link after a while, the link will no longer be valid. This also means that you can't simply pause the download and start it later, unless you obtain a new download link from the site (by clicking on it once more and grabbing the URL) and input that into the accelerator.

The GOG download manager circumvents this by being logged into your account as it downloads, so it can get new download links on its own. You can also just download from the browser with no accelerator, but again without pausing the download.

I think this may be the cause of what you experienced.