Sounds like a combination of filesystem issues along with the unusual scripting you set up to automatically boot the OS4 partition. You can eliminate the latter variable by forcing an OS4 boot partition in the Kicklayout:
At the end of the Kicklayout file, you'll see an entry for Kickstart/BootDevice. Make sure it's enabled. Now create a plain text file called BootDevice in the Kickstart directory of the OS4 partition. In it, type the partition's device name. Mine says OS4
because OS4: is my OS4 partition (took me a long time to get this right, believe it or not!).
See if that helps at all. If not, come back and we'll diagnose some more.