1. Make sure all of your apps are synced with itunes
2. Select ‘Deathorize Computer’ from the store menu, enter your password…** DONT SYNC NOW!!!
3. Now select ‘Authorize computer’ from the store menu, enter your password and click the sync button (even if its grayed out you should still be able to click it)

This worked for me, apparently when you update the iPhone firmware it screws with the DRM. By doing this (deauthorize, authorize, sync) it reauthorizes the phone.

Spent the last 6 hours trying different solutions, restoring, resyncing, updating, rolling back and this took all of two minutes in the end. Just glad I didn’t lose 6 months of gym data by having to reinstall my GymBuddy App!!!!

Hope this helps someone out there.

jailbreak users, kill safari via “Processes” in SBSettings and then use the “free up memory” command. This almost always frees up enough memory to run the app in question.

non-jailbreak user, instead of the slide to reset (“soft reset”), do a “hard reset”. I have been informed that this clears the memory much more comprehensively as it completely restarts all processes. To do a “hard reset”, press and hold down the home and sleep buttons and hold them. Ignore the “slide to power off”, keep holding and it will eventually reset. You can then turn your phone back on in the normal way. It will takes a bit longer to boot than normal but when it does finally boot up, you have a fresh, completely clean boot.