Version: 1.4.2 (using KDE KDE 3.4.3) Installed from: Ubuntu Packages OS: Linux When you have more actors above each other in a usecase diagram, using the same use case, and you want to align the usecase vertically in the middle of the two actors, the actors are put on top of each other instead of remainig aligned above each other, schematically like this: Actor--Use case / Actor / when aligned vertically results to this: Actors--Use case instead of this: Actor\ Use case Actor/ (I don't know if the spaces are saved, but I hope so :) )
The function "Align vertical middle" is only useful for widgets in a row that are to be aligned vertically. A better-aligned alternative is to use the "Apply Layout" function from the use case diagram context menu.