After investigating the problem for some time, I manage to narrow the problem to my customized theme. I'm not sure if it's my fault or it's a bug since I'm using the same "theme.scss" file in both versions.
Looking at the theme.css (my customized theme), as for 4.0.7 the mentioned resource is addressed like so:
It reveals the problem clearly. I'm just not sure if I did do something wrong to end up with such addresses! All I did was to copy my theme.scss file by config.rb's side and execute the "compass compile" command. Just as the same as I did for 4.0.7.