DP5 quits immediately after trying to save a file: "Error while writing...

DP5 quits immediately after trying to save a file: "Error while writing to the drive. File created in a later version of DP and cannot be opened in this version. Try to save your file to another disc or folder, or with a different name."

There was a problem with DP's authorization process. Fix this buy repairing disk permissions and forcing DP to reauthorize.

To do this:

Delete the hidden authorization file:
• Go to /Applications/Utilities and launch Terminal
• Type: cd / and hit Return (mind the space between cd and /)
• Type: sudo rm -R Auth-DigitalPerformer\ 5.0 and hit Return (mind the space after the \ and 5.0)

Repair Permissions:
• Go to Macintosh HD > Applications > Utilities and run Disk Utility.
• Click on the First Aid tab, select your hard drive from the left, and hit Repair Disk Permissions.
• When that is done, reboot your machine.

Then Re-Authorize:
• Insert your Digital Performer 5.0 disc back into the computer and then launch DP5.0.
• DP5.0 will prompt you for your key code to reauthorize.