Hello, fellow Mac users!
This issue hasn't been fixed yet, and whilst you wait, I thought that it would be nice to provide a tutorial on how to fix it.
1. In Finder, go to [User] > Applications.
2. Find Marble Blast Platinum.
3. Right click (or hold down control and click), and a menu will appear.
4. Select "Show Package Contents".
5. Double click the folder "platinum".
6. Double click the folder "data".
7. Make a new folder (inside "data") called "interiors".
8. Open up "interiors.zip".
9. Open up the folder "interiors 2", which should have 872 items in it, and not 0.
10. Select the files "checkerboard2.png" and checkerboard3.png". Please note that these are the .png files and NOT the .jpg files. They should look the same. This is important, because if you select the .jpg files, it won't fix the issue.
11. Copy "checkerboard2.png" and "checkerboard3.png".
12. Go back to the folder "data", and double click the folder "interiors" that you just made, that should have 0 items in it.
13. You should now see a blank screen, which is displaying the contents of "interiors". Paste checkerboard2.png and checkerboard3.png there.
14. Open checkerboard2.png (it should open in Preview). Go to File > Save As. You may have only Save. In that case, hold down Option, and Save As will appear.
15. Save checkerboard2.png as a .jpg file.
16. Do the same thing with checkerboard3.
17. You should now have four identical looking files in the folder "interiors".
18. You can go back to "data" and delete "interiors 2".
19. Now run the launcher and Arrival to Marbleland will work. Have fun!
Credits to Pro Marbler for initially telling me how to fix this.
