MacOS – /StartupItem/ Error, How to resolved the issue

I ended up bringing my Macbook Pro into the Apple store. The genius there attached the store's OS X Snow Leopard via USB, and booted from it, and ran the Repair Disk, which gave the same error of an invalid node structure. Since it was still under Apple Care, I got my hard drive replaced and was able to keep the old one.

With the new hard drive, it had Snow Leopard on it, and I simply upgraded it to Lion without a problem. I was able to attach the old hard drive via USB, and restore all my files.

Thanks everyone for their help. +1 to everyone.

This problem may be the result of failing RAM or a failing disk drive or potentially some other hardware problem.

It should really not take more than 5 minutes to boot a mountain lion compatible Mac in the worst case.

1. Check how much RAM OS X thinks is in the computer Apple Menu > About This Mac. Make sure it is the amount your expecting, for example if your computer when you bought or upgraded it it said it had 4GB of ram make sure its not showing that there is some different smaller number.

2. Run a Apple Hardware Test for your Mac.

3. Try running a memory test program, something like memtest

4. Back up your important data

5. Try running a disk testing program, something like TechTool Pro

If all the above fails to uncover a cause try a clean install

1. Make sure you have a boot-able Mountain Lion Installer, etc or have an internet connection and a "OS X Internet Recovery" compatible Mac

2. Erase the disk drive, and re-install a clean copy of OS X.

3. Use the machine for a while, and see if the slow booting problem returns( if there is a problem with the disk the issue should return after indeterminable time). If the problem does not then this would fix it.

4. If the problem does return I would try a different internal drive to boot the machine with, in order to determine if the problem is with the drive or with the mac.

5. Repair / replace the failing hardware, note that parts may be covered under Apple's Warranty.