I'm going back to SP4.0 (again -- 3rd time). I've got two very similar parts with identical loft cuts in them which rebuild differently. I've also got a part which shows no rebuild errors, and if you delete or suppress the very last feature (a simple fillet feature) half the Feature Tree goes red. SolidWorks QA has still got a long way to go before they can put out a service pack without regressions.
Mark 'Sporky' Stapleton Charlotte, NC