MacBook Pros can't run iOS 7. Please edit your signature to correctly indicate what operating sytem you are running into the problem with, or state what it is. Also, note many a USB Stick has a write protect tab that can be switched and affect the ability to write to it. Also, if you format a USB Stick NTFS, the built-in Mac OS X software doesn't support it for anything else but read-only. Addon software exists to write to NTFS. FAT32 and ExFAT, and FAT16 are all supported on Mac OS X 10.6.5 and later. Lastly if you are using multiple USB devices on the same bus, which the System Profiler can reveal if you are, they may slow down or cause interference with data transfer with your USB drive. Make sure to isolate the device to its own bus, or get a direct to wall powered USB hub to connect it to.