Make sure your sdcard is mounted when unlocking... and you have the free app installed.
You need to download the free version first. This is just unlocks the free version.
Note 12 Nov: Regarding the bad comment below - we make every attempt to make sure the app is bug free - from time to time things go wrong - her problem was very easily fixable. We are always happy to help - so just get in contact - there is a link in settings.
There is a full upgrade and rewrite in progress the app will be more expensive after the new version is released - so now is the time to save yourself a couple of bucks.
If you like it please take the time to leave a comment ... it *really* is appreciated.There is 17.5% VAT charged to European users, sorry.
http://www.my-pod.org/faq.php for questions or comments.
Note this version doesnt hav to be the same as the version of the free app you are using - it is not released as often.