Error 500 when adding a condition

When I follow these steps I get an Error 500:
1.-Create a webform with two elements: 1 textfield, 1 select options.
2.-Activate events for it.
3.-Create a new rule.
4.-React on event: Rules Forms => Webform is submitted.
5.-Add a condition: Rules Forms => Form element has value... => textfield.
6.-Set the value of the textfield.
7.-Save... => ERROR 500

I also get this same error when I try to edit/clone the rule once created, I can only delete it. I've tried the dev version with same results. Other events or conditions are working correctly in Rules.

I'm using a fresh install of Drupal 7 (all the modules are updated).

Am I doing something wrong?