Yes, I've backed up my save to PS+ storage area. One time after crashing, the game told me that my save file was corrupt, so I downloaded my file from PS+ back to the system.
The error I've been getting is C2-12828-1.
This page said that it could be caused by "invalid processing on the application side" and might result in a corrupt save file.
A few minutes ago, I decided to delete Joe Danger, download the game again from PlayStation Store, and start over with a fresh save file. After finishing the first level, the game bombed out while tallying scores at the scoreboard.
I repeated this entire process (erasing the game and downloading it again), and the same thing happened
again at the score tally for the first level.
I've removed the game from my memory card again. I'm really not sure what's causing this, but I can't continue to waste time "trying" to bypass it. It's possible that the memory card is corrupt (I sure hope not), but none of my other games have presented a problem like this.