Try using the LOAD function to open the sequence in question from a new Project.

1. Create a new project.
2. Choose LOAD from the FILE menu. A standard Mac "Open" Dialog appears.
3. Click the file containing the sequence you wish to load, then click Open.
4. In the LOAD dialog that appears, make sure "Load Chunks" and "Data" are selected.
5. Click the sequence inside the dialog box you wish to load (it will most likely be named "Seq-1") so that it is highlighted.
6. Click OK.

The sequence you loaded will appear in the project's "Chunks" window. What you'll probably see is TWO chunks labeled "Seq-1". Play enable the one that is not currently enabled, and double-click the name to open it.

Manual reference: Page 17 of DP3 and DP4 User Guides.