You can split a project in two by doing this.
1) Go to the Project Library View.
2) Select your project, and click FILE/DUPLICATE PROJECT. Give it a name like "your project name - part 1".
3) Do this again. This time name it "your project name - part 2"
4) Open Part 1 for editing. Delete everything in the second half.
5) Open Part 1 for editing. Delete everything in the first half of the project.
At the end you should have your original project, plus the same project in two parts.