Firefox ignores requests to open a webpage

[sclaes]

Sometimes when I enter an URL in the address bar, Firefox completely ignores this and refuses to open the webpage (the URL of the previous loaded webpage reappears in the address bar and nothing happens). There is no problem with my internet connection because I can open the webpage in a new tab (i.e. when there is a link to that webpage on another webpage I can right click on it and open the webpage in a new tab).

This only happens when the NoScript extension is active.

I have no idea if this is relevant but I have many, many tabs open on a lot of windows.