Never, ever pull a drive without halting it (in XP, right click on the "green arrow" icon in the system tray and say "Stop"; on OS X, eject the drive from the Finder). You may have gotten lucky before, but you're asking for it.
Zar, you may have shorted the drive. Alternatively, it could be the port -- try putting it in the other one, or closer to the main machine instead of into the keyboard hub. If that doesn't work, what you can do is plug the drive in, start Disk Utility (go under Applications; it might be in the Utility folder) and see if it's listed in the left hand list of devices. If it is, try mounting it. If it won't mount, try formatting it (at least you can get it working again). If it doesn't show up at all, you may have just made yourself a new doorstop.
"you're a doctor.... and 27 years.... so...doctor + 27 years = HATORI SOHMA" - RoyalWing, when I was 27
"Al hail the forum editting Shooby! His vibes are law!" - Osaka-chan
I could still be champ, but I'd feel bad taking it away from one of the younger guys. - George Foreman