I'd guess you were both running different IOS revisions, his being a bit newer. You can run Signcheck or DOP-IOS (or even DOP-IOS MOD) to check which versions you both have. Signcheck will export it's findings to an excel document on the root of your SD card. Compare your IOS lists with This List to see if there are any which need to be updated.
If there are, you can use DOP-IOS or NUS Downloader to get them.