Try dragging your task bar and dropping it at the bottom before opening
Firefox. The buttons may be hidden under the taskbar.

still did not work.,....what is unusual is you normally can
click on the top bar and minimize and such but all it gives is tool bar
options.

system>preference>screen resolution is one possible answer

Try a different resolution! some times without our desiring it a
program may change the screen resolution. try a resolution with a
larger number for the hight of the screen.

Of course I am assuming that your FF window is maximized. If the
window is not maximized try maximizing the window first (full screen).

Under preferences you will find "windows" that give preferences for
your open windows. Look and see what key you need to press and grab
the window with your mouse. Then grab the window and drag it down to
access the windows top bar.

This is the same problem that I have only it's not limited to firefox
with me - the min, max, x close is gone from everything, all
applications, all files, even pop ups !!!!

No solution so far.

This is quite a strange problem. I have had the same
happen to me on a couple of occasions for no obvious
reason but the title bar has come back when I reboot.
I have not been able to recreate the problem with any
settings so I can't track what causes this to happen.
I'm using Mint Elyssa which is basically Ubuntu 8.04.