NB: instrumented build 200710232304

Repro steps:
1) Create 2 projects (P1, P2), a class diagram in each project (Diag1, Diag2)
2) In project P1, create 2 class elements C1, C2
3) From the project tree in P1, <Shift> click to multi select C1, C2 at once and drag them
   to project P2 Model,  select No to the move dialog
4) Expand project P2 -> Imported Elements, C1 and C2 now shown in Imported Elements
5) <Shift> click to multi select C1, C2, and press <Delete> key 
   "Delete Imported Element" dialog appears, select Yes

   Notice only 1 element was removed from the imported element list though 2 were selected.