Hey, if the PlayStation Store says "This Service Is Undergoing Maintenance", or something along those lines, you can perform the following steps to try and address the issue:
Navigate to PSN > PlayStation Store, press the triangle button and choose "Delete". After deleting the PlayStation Store, restart your PS3 system and then navigate to PSN > PlayStation Store, press the "X" button, and re-install the application.
Navigate to Settings > Date and Time Settings > Date and Time > Set Via Internet. If the time isn't correct, then you may encounter this type of error on the PlayStation Store.
(Keep in-mind that these steps only apply to the PlayStation 3 system)
Thank you for this post. I have been having this issue for a week now, but un-installing/ re-installing helped me out (after 2-3 times). I hope everyone else can get theirs sorted out soon. This issue has been so frustrating.