This behavior doesn't happen with an old version I was using on a netbook running version 2.9.0.4.
I thought perhaps it was due to the HTTPS upgrade in whitelisted sites, but that wasn't it as the site in the netbook wasn't added to the white list.
The behavior happens if NoScript is disabled allowing basic protection or turned on completely. There's something in this latest version that causes the loading indicator to spin constantly when you access a password protected webpage.
Here is a screen shot of the password protection for a FTP folder I'm referring to.
