Or is the problem on the next page where you have the login form?
Some add-ons have programming errors that can cause the upper part of the page to be blocked, i.e., that part of the page never detects that your mouse is over it. If you think that describes some of your problem, try disabling ALL nonessential extensions here:
orange Firefox button or classic Tools menu > Add-ons > Extensions category
Then restart Firefox and test again. Does that make any difference?