A newly discovered bug causes most Mountain Lion apps that use text fields to crash if you enter a local file's URL in the text field.
For example, entering "File:///" (without the quotation marks) in a text field causes many Mountain Lion apps to crash. (The letter "F" in the word File must be upper case.) The crash may occur after you enter the third forward slash or not until after you press the return key.
According to NextWeb, the crash is caused by data detectors, a feature that allows text to be recognized as certain types of data, such as URLs or email addresses.
For the most part, this type of app crash is nothing more than an inconvenience, and shouldn't cause too many problems. However, if you have an app set to automatically restart, or to restore the last window that was open, then you could get stuck in a loop of the app opening after crashing, restoring the window that contains the File:/// text, and then crashing again.
The workaround is to start the app. If a dialog box tells you the app crashed the last time it was run, and asks if you want to open the window again, click No. (Many of us automatically click Yes without thinking, and that's what gets us stuck in a loop). This will let the app open without restoring the last window.