When working in a Central or Local file you will find that you cannot finish a stair sketch if you sketch Risers first then Boundaries. This assumes you used the Riser and Boundary tools instead of the Run tool.
Strange but it makes no difference in a stand alone project but seems to matter a great deal in a central/local file. The workaround at this time is to sketch your stair Boundary completely first then add the Risers.
Here is the familiar error message dialog that you'll get if you sketch poorly.
Sketched poorly perhaps in some cases except that I have and several students have encountered this message while learning stair features and using worksets at the same time. At first we attributed the errors to basic sketch mistakes. Then we started to think maybe upgraded templates might fail to produce the stair. In the face of repeated tries as well as in brand new stock templates it became obvious that it was deeper than simple sketch mistakes or upgrade issues.
Revit support isolated the behavior to the order described above because they are accustomed to Boundaries first, Risers second and this process didn't generate the error. I'm not sure when this behavior crept into being but I know that it is present in Revit Building 8.1, 9.0 and 9.1, just tested it in those versions, so it has been with us for awhile. The image depicts a "U" stair but this issue will appear in any stair shape other than a single straight run, those will finish without error messages.
At the sign post ahead is "The Quirky Zone"...you've been warned! 8-) If you've encountered this at some point and thought you were crazy, you may be, just not about this!