I've been getting the same thing. It says the app failed, hit PS button and retry but it just says the same thing every time. I updated to the new store last week but haven't been able to get on since. I can use the browser and play online games still.
I saw somewhere else on here to check the date on the ps3. Mine was set a year ahead because of cinavia blocking a movie. Well I set my date and time to the correct setting and now the store works again. Hopefully this helps someone else