Could it be... Satan? seriously, Apple's engineering teams must have a contract with the devil requiring them to make as buggy and inconsistent a product as possible. I see the same issue, often. All AST2 resources are up to date on the local diagnostic server, but it doesn't matter. Like you say, sometimes a PRAM and SMC reset will help. Last time this was a consistent problem at our shop, apple tech troubleshooting chat couldn't find any way to fix it except telling me to format and set up our whole AST2 server machine again from scratch. The one from today (because of which searching for the adtm error led me here) refused to run any OS-based diagnostic over ethernet, but it did succeed in going into OS diag mode when run over wifi.