The simple steps you need to take to fix the ‘Nice Try.’ error message on your Textpattern/TXP installation are:
* Login to your control panel
* Go to Admin
* Go to Preferences
* Go to Advanced
* Change the Maximum URL length (in characters) to a higher value til it works!
I think it was put in there to stop people trying to hack URL’s but as the modern world of Mail campaigns seems to add a whole host of GET variables it’s pretty easy to overrun this limit.