title: I can't enable or disable modules. I'm getting "An error occurred while saving this configuration"
body: <p>I have a new fairly fresh install of Magento 1.7.0.2. I installed two custom payment method modules that are working fine. But now whenever I try to disable or enable any Payment Method or Shipping Method it gives me an error like this:</p>
  
  <blockquote>
    <p>An error occurred while saving this configuration: Warning:
    preg_match() expects parameter 2 to be string, array given in
    /app/code/core/Mage/Adminhtml/Model/System/Config/Backend/Encrypted.php
    on line 57</p>
  </blockquote>
  
  <p>Do you have any idea why? </p>
  
  <p>EDIT 2:</p>
  
  <p>I found the problem. It was caused by a patch I applied to fix to a previous BUG. :P</p>
  
  <p>EDIT:</p>
  
  <p>So I disabled all custom modules and I was still getting the same error. I logged what was happening and it seems that some core modules are sending an array to be saved. </p>
  
  <p>Like PayPal Express Checkout for instance. One of the config options is the Time of Day in the SFTP credentials for Settlement Report Settings. It's composed by three different drop-downs and it's sending an array to be saved! </p>
  
  <p>In the Shipping Methods, UPS has a config options called Allowed Methods, and it's also sending an array!</p>
  
  <p>I still don't know why it wasn't happening before and now it is. They shouldn't be encrypting everything. Any clues?</p>