from time to time when browsing in firefox, when clicking a link or a bookmark, the tab will say "connecting" for a moment only to abruptly stop and leave me on the page I was already on, as if my browser 'forgot' what it was doing or to take me there.
I've taken it up with Mozillas support forums, but it's very hard to test what's causing since it happens totally at random, sometimes several times in a row, sometimes it'll go hours without doing it. One mod suggested Avast's url scanning might be to blame, but I'm a little hesitant to just brows for hours without my webshield on to test it