DNN version 7.3.1 (upgraded a few times)

I have a brand new portal on an instance with about 4 other portals.

I've set the Logo in the Site Settings and I've got the DNN skin with the Logo skin object.

But when the page loads, the image isn't there because the paths looks like this:

<img id="dnn_dnnLogo_imgLogo" src="//Portals/mysite/bca-logo.png" alt="Community Association" />

The double forward slash is wrong. It should just be a single forward slash before Portals. I also noticed that this problem affects the favicon.

<link rel='SHORTCUT ICON' href='//Portals/mysite/Images/favicon.ico' type='image/x-icon' />

The other portals on the instance don't suffer from this problem.

Any idea?