I was just updating to v1.4 and I saw a message basically saying that wp-super cache wasn't working before and it fixed itself. I then tried to navigate to the another page and got an error from wordpress saying it couldn't connect to the database.
Upon further investigation, I discovered that an unclosed comment in wp-config.php was effectively making the database name commented out (hence why it couldn't connect). The first part of the unclosed comment originated directly before the code that your plugin inserts into the wp-config file. After closing the comment, everything works as expected.
This happened both in mamp and again on a live server. This needs to be fixed asap, since I'm sure not everyone using this plugin has ftp access or even knows how to diagnose this sort of issue.
FYI I know this is an older version of wordpress, I was in the process of updating everything when this happened.