I've had a couple e-mail messages from other D-20 users about a strange error with the synth, so I thought I would post my own solution here. This is kind of involved, so if anyone has an easier way to recover from this, please let me know. Please also let me know if you know of the actual reason the D-20 does this.
The best description of this is when you turn on the synth, you will see the display screen light up with all characters on the top line light up, but the bottom line of the display will be dark. They keyboard is completely unresponsive with only the power switch working.
I found that if I left the keyboard on for a while, it would finish booting up and would play normally, but then after turning it off and back on again it would do the same thing. I was able to get the keyboard fully functional again by doing a full reset. You will need to open it up, take out the backup battery and let it sit for a little while, maybe an hour or two. Put the battery back in after that and initialize it when you start it up again. Make sure that you are comfortable both opening the keyboard and locating the battery as well as backing up your data and know how to initialize they synthesizer. I have posts describing all of this, just search for D-20.
I've been lucky since doing this, the keyboard has been behaving itself. It really is no fun constantly opening and closing the keyboard body, so if you do have an easier way to deal with this freeze definitely let me know.