portable hard drive suddenly not being recognized :(

Help! I hope you guys can figure this out. I've been using an 80gb smartdisk firelite portable hard drive for years now. I haven't had any trouble whatsoever with it on the macbook before. I was in the middle of watching an episode of anime, when the episode froze (the file was stored and being accessed from the portable hard drive).

The HD was plugged in, all cords attached, and still running (it is powered by its connection to the Mac). The power setting was still switched on USB (if changed to external it shuts down its connection to the computer).

I ejected the hard drive using the Mac commands. I plugged it back in, and the hard drive came to life power-wise. I can see the power light on and feel/hear it functioning. But the Macbook does not recognize it. The icon for the hard drive does not appear on my desktop, in the finder window, nor can I search for it using the search functions. I unplugged it manually and plugged it back in, reset the computer a bunch, and still no luck.

I have no clue why the computer ceased to recognize the hard drive. I don't think it can be an issue with the hard drive itself, as all connections with it appear to be okay and it seems to be powered as normal. But this is just speculation, I guess. I can't test it on another computer. I live alone in a studio apartment and only have the Macbook.

Anyone have any ideas? I am scared to lose everything on the hard drive ... especially if I can't even access it anymore. Help help!

Have you tried turning your mac entirely off then on and see if it mounts it then?
Try another port on the Mac?

Are you allowed to hook it up to a Mac at your local Mac shop to just test?