I apologize for this somewhat long story. About a month ago, my computer kernel panicked. I was running Mavericks at the time and had no problem using iTunes. I did everything I could on my end to try to fix it, including erasing the hard drive and attempting to reinstall, but nothing worked. I took it to the apple store, where the genius reinstalled Snow Leopard on my computer. iTunes ran fine on Snow Leopard, but I recently upgraded back to Mavericks and have not been able to use it since. When I try to run it, it says, "To run iTunes in 64-bit mode, select the iTunes application in the Finder, and choose the 'Get Info' command in the File menu, and uncheck the 'Open in 32-bit mode' checkbox in the iTunes Info window." Why is this happening? And how can I fix it?