Hmm.
Again I say, hmm.
What machine are you using (the Titanium or the Aluminum)? What OS? Have you successfully burned CDs with iTunes before? Can you successfully burn a CD in the Finder? Do you have AppleCare?
The most likely thing is that your CD-RW drive itself is kaput. There are other potential reasons - several bad CDs in a row, a dirty lens on the CD drive, software problems, firmware problems, unholy curses...
BTW, how did you restart? Using the Cmd-Ctrl-Pwr trio? Or going to another program than the Finder and choosing Restart from the Apple menu? Holding down the Power key for five seconds? Do you know that you can Quit the Finder (which will start again; just the app, not the whole computer) using the Force Quit pane?
Finder will have difficulty ejecting while iTunes is using the disc. Is iTunes frozen as well?
Now, this is a lot of questions. Most of fixing problems just involves going through all the possible situations, and the answer appears without mucch sweat.