Since the OS 3.0 update, I accidentally restored my phone to factory settings – I don’t even know how I managed to do that! Unfortunately I had also recently reinstalled my operating system, so none of my applications were stored in iTunes. “No problem”, I thought, as I trawled through my purchase history and downloaded a bunch of applications in iTunes (and accidentally purchased a few I thought I had).

Once I had finished I turned on application synchronising in the iPhone settings, and hit the big “Sync” button. “That finished rather quickly”, I thought.

After fiddling with settings and restoring the firmware once again, I figured out how to sort it.

1. Click the store menu
2. Click “Deauthorise computer”
3. Enter your account credentials
4. Once finished, click the store menu
5. Click “Authorise computer”
6. Enter your account credentials again

After doing that I was able to synchronise my aplications from iTunes to my iPhone without any problems.