[pslade]

Steps to reproduce:

1. Create new project plan
2. Add 1 group with 2 child tasks
3. Set each child task to 50% complete (any % will do)
4. Group % complete will show 100%
5. Save plan and exit
6. Open plan
7. You will see that the group is now showing 0% complete. You will have to un-group and re-group for it to total (and it will be lost again on next open).