I should mention that I have crashed (yes, crashed) the system twice today already. Once by clicking "Calibrate" in the Displays settings panel (color tab), and another time by choosing "Get Mac OS X Software..." from the Apple menu.
In both scenarios, I tried Opt-Cmd-Esc and force-quitting, and in the first case it only locked up tighter, and in the 2nd, the 3-key combo had no effect at all. I ended up with a 'spinning disc' cursor, unable to do anything.
firstly, open the application from the Application/OmniWeb directory. It will then appear in the Dock.
then, right-click (or control-click) the icon to get the pop-up menu. choose Add to Dock (or whatever it's called). it should stay in the dock from then on.
btw: you did remove it from the Disc Copy app, right?
Also, when you think you've locked up try clicking on other X things. items in the dock, other windows, etc. if they come up then you haven't actually crashed anything other than the app that you were in.
use the Apple Menu/Force Quit... feature. it should behave the same as the 3-fingered salute, but at least you know that you are actually alive and well.
Force Quit now brings up a windows-like app listing where you can choose which app to kill.