I have a set of about 10 Sales Order that did not create Revenue Arrangements. What I know is a) The same customer & items created Rev Arr last year. b) The Items we are using have the same Rev Rec rules as all our other items c) The SO lines have valid Start & End date combinations. I've compared successful SOs to these 10. Where would you guys look next?

In general I'd go to the Jobs Screen for Rev Arrangement processing (the name of that screen escapes me now) whenever you have an issue. The jobs should show as failed and it will give you why. Like all NS error messages, it's sometimes more useful than others, but something like an invalid department should have thrown that "invalid reference key for department 1234" error.