the latest build/patch installs HydroCAD 9.10
I had 10.1 on the computer, it overwrote some files.
No big deal, I just re-installed HydroCAD 10.1, but this may create a moment of panic for some users when a hydro-cad model will not run do to new features in HydroCAD 10.1 that are not available in 9.10