I have also encountered this error and each time my .dbc was corrupt in some way. The first time I had duplicate views in the dbc as well as a partially deleted view so I was forced to manually fix the dbc entries. The second time the .dct file was invalid. When I issued VALIDATE DATA I recieved the message on the status bar 'Memo File damaged. Continue Processing' but apparently it did validate. On Pack DATABASE I recieved error 1538. On looking at some of my tables in my DBC I found that they had corrupt entries and the also had duplicates on a primary key (integer). They were all zeroes. After manually deleting the corrupt records in the tables, reindexing the tables, I was able to properly validate and pack database.