Application and system prefs errors after restoring user

When I try to open a few of my applications, I'm getting this error message: "[application] cannot be opened because of a problem." And something about check with the developer for compatibility with this version of OSX. This is happening with all the iLife apps and Mail, as well as Logic 9.

I'm also getting an error when trying to open certain panes of system preferences (https://discussions.apple.com/thread/5082670?start=0&tstart=0).

Unfortunately, every time I search up help on this issue, I can only find topics regarding Lion and Mountain Lion - but I am on Snow Leopard and this is happening!

Recently, I went through a process of renaming my main user, by deleting it but keeping the files, changing the deleted user name, and restoring the user: https://discussions.apple.com/thread/2302635?start=0&tstart=0.

Everything else seems to work fine, except for these 2 problems.

I have already: (a) Unchecked 32-bit mode for system prefs, (b) Deleted proper prefs files in the Library (com.apple.prefs....), (c) Tried launching apps from terminal, (d) Tried deleting aliases to apps and restoring them.

Nothing is working! I am about to back-up my system and re-install Snow Leopard, but I wanted to explore other avenues first.

Thank you!