APM SSO -Kerberos Decrypt integrity check failed

Hi, Daniel. I'm working with Gulfam on this. We've setup APM and SSO already using other methods and everything is working fine. Also, we've setup Kerberos on the back-end servers and, again, all seems to be fine - a Domain user can logon via Kerberos SSO to that back-end web server. Now, in regards to this problem, this is what I can add: We followed the "APM Cookbook: Single Sign On (SSO) using Kerberos". The TGT seems to be fetched by the F5, as well as the ticket for the xpto@DOMAIN.COM account. However - and this is what we think is the problem - the F5 cannot decrypt the ticket for some reason. Any hints on this? TIA! -- Miguel