So the text string "File:///" can inexplicably crash just about any app on Mountain Lion. Aside from being a curiosity, it can also be a weapon if you start hurling File:/// salvos at your friends through iMessage. If you get hit, or you hit someone and feel bad afterwards, here's how you can fix the damage.

If you get crashed with a message containing that string, you may notice that iMessage just keeps rebooting. That's because that string is still hiding in your history. We have to get rid of it. First you have to make your User Library visible:

- Open a terminal window
- Enter "sudo chflags nohidden /Library/"
- Press Return
- Enter your password when prompted.

Once you've done that, the most sure-fire fix is to delete your entire iMessages history:

- Quit iMessage
- Hit Command+Shift+G and enter
- Enter " /Library/Messages/" in the Go To Folder window that appears
- Take all the "chat.db" and "chat.db-*" files and put them in the trash
- Empty the trash
- Restart iMessage

In the meantime, just hope your prankster friends aren't savvy enough to know they can crash your iMessages with just a couple of characters. Either that, or get them before they get you. [Thanks Steve T-S and Manfred Scheiner!]