Symptoms

The following error is being logged very frequently on K2 servers within K2 NLB farm:

Event code: 3012
Event message: An error occurred processing a web or script resource request. The resource identifier failed to decrypt.
 

Diagnoses

This error normally occurs when static machine key has not been configured to be the same for all servers within K2 farm. Refer to the following section of K2 documentation for details:
https://help.k2.com/onlinehelp/k2blackpearl/icg/4.7/default.htm#troubleshooting_nlb_setup.htm

Essentially when you have multiple servers within K2 farm you have to configure IIS to use the same static key on all servers. In order to do that you have to uncheck Automatically generate keys at runtime both for validation and decryption key and click on Generate keys on the right side of IIS console. Next you should uncheck these checkboxes on other nodes, but instead of generating keys you have to paste key values from the first server on all other servers.
 

Resolution

See details above.