Yes, I have had this issue as well. It appears that when the OS gets hold of a DVD it can't read (due to a defect in the disk or something), instead of behaving itself and kicking the disc out with an error, it goes into the spinning beach ball of death. This issue has thrown me into a rage more than one time. Sometimes I am able to force quit DVD player and reboot, but often the hard reset is the only way.
A few suggested solutions:
1. When it happens, try force quitting DVD player, then rebooting your system. To force quit, press command-option-escape (the command key is the one with the apple on it). Then choose DVD Player from the list and choose force quit.
2. Stop using your mac for DVD playback. The software is clearly buggy, this will prevent the problem.
3. Stop using macs entirely. I have had several applications written by apple do this to me - DVD Player and Time Machine are the most recent two. This will prevent apple-created apps from bringing down your system.
I am only partially kidding about 2 and 3. The spinning beach ball of death has me seriously considering a change in platform.