Saved Search with a Filter that uses Credit Card Number field Expressed in a Formula > Notice: Your formula contains a reference to an encrypted field. This is not allowed.

This is an intended change in line with increasing the security of customers' credit card information.  Credit Card Number field when added as a filter on saved searches is now limited to: is empty or is not empty.

Actual complete email sent out to customers last December 16, 2013:

"Change to Credit Card Number Search Criteria

In an effort to increase the security of your customers' credit card information, beginning on January 9th, 2014, search criteria based on the Credit Card Number field will only be able to use the following operators: is empty or is not empty.

Existing saved searches that use other operators (like is or is not ) with the Credit Card Number field will be deleted from your account after this date.

Additionally, any credit card number searches executed programmatically through Web Services, SuiteScript, or SuiteFlow that use disallowed operators will no longer work.

We have identified searches in your account that will be affected by this change. To continue using these searches, you must update them to follow this new requirement. If you have any questions, please contact NetSuite Customer Support.

Thank you,

The NetSuite Team"