that's because linux mint "is" ubuntu (as in, it's derived from ubuntu). the issue is probably something related to your hardware not being supported properly. what are you running this on?
and what exactly do you mean by the "the text boxes close and the "next" and "Cancel" buttons simply stop workng "? what you should be seeing is a window which, depending on what you're trying to authenticate, either shows up on the screen with a minimize/resize/exit window bar that is always on top or a splash that is centred in the middle of the screen and darkens/disallows access to the rest of the desktop until you either select continue or cancel. for either of these, typing in your password and hitting enter (or pressing the button that is not cancel, as the text on the other varies according to the task being carried out) should make the window close and the task you were trying to carry out continue as it was.
as for the password on echoing in terminal, that's standard for -nix in general.

if you're really having trouble there are plenty of different distro's in the sea. distrowatch like albert mentioned, is a great place to find alternatives. as a general rule, you should always search online to find other people's experiences when installing a distro on your particular hardware to find out beforehand if there are any major problems.

as for ubuntu being buggy, i've been using it for a while now and have encountered a sum total of two buggy situations, neither of which caused the machine to crash and both were easily fixable through rebooting. i've screwed myself over when messing around plenty of times, but that's always entirely my own fault and is almost always fixable via online help, either through posts from days long gone or, if none exist, new threads in support forums. after having run both mac and windows software on this same machine before switching to ubuntu, i'm very happy with the additional freedoms, even if they include the freedom to break EVERYTHING , and i've actually had a much more bug free experience.