Is there a workaround for this problem in SWX2010SP2.0?  I've imported a PCB profile from EasyPC (stop laughing!) and the sketch needs a bit of tweaking before I can extrude it into the shape of a circuit board.  If I delete a sketch entity, then decide perhaps I want the deleted entity back, there is no undo function!

Also, if I drag an entity, decide to undo the drag, the undo function is greyed out.

Why?