Version:           2.2.3 (using 4.2.3 (KDE 4.2.3), 4.2.3-2.fc10 Fedora)
Compiler:          gcc
OS:                Linux (i686) release 2.6.27.21-170.2.56.fc10.i686

When copy use case entities and actors in the Use case diagram Umbrello is doing a shared copy of them. In result when user edits the original use case the copy is editing too. I suggest it will be better if Umbrello would do the deep copy of the use cases and actors.