I still use 2006, and often make maybe 5-10 configurations of a part which has optional features, and in the part solid, there are times when I finish and everything is OK (no Red) and I go to the assembly, and the part then has an error. The worst offender seems to be a sketch which is in a Supressed feature, which turns 'On' (but not the Feature made from the sketch). Once I Supress the erant Sketch, all is well, though sometimes it does the same thing over again. Anyone else see this? Anyone know why it happens? Am I mistaken, or do configurations need a bit more work? Thanks - Bo