I have been using Spark 2.5.8 with Openfire 3.6.3, XP SP3 and SSO on our domain for a long time now with no problems. We are planning a Windows 7 upgrade and I decided to test Spark 2.6.0 as part of the Windows 7 deployment but I cannot get SSO working. When I try to login I get the error “Unable to connect using Single Sign-On. Please check your principle and server settings”. If I upgrade an existing working XP client to Spark 2.6.0 I get the same error. The only thing that is changing is the Spark version which seems to break SSO. When I check each clients SSO settings under the Advanced - SSO tab, version 2.5.8 reports the Desktop Account as “USERNAME” where as version 2.6.0 reports the Desktop Account as USERNAME@DOMAIN_NAME.LOCAL. This is the only thing that I can identify as different between the two versions. Please help - any advice greatly appreciated.