NB: instrumented build 200710232304

Repro steps:
1) Create 2 projects (P1, P2), each with a class diagram (Diag1, Diag2)
2) In project P1, create 2 class elements (C7, C8), add them to Diag1
   In project P2, create 1 class element (C9), add it to Diag2
3) Click Diag2, DnD C7 from P1 to diagram Diag2
4) Add a navigable association from C9 -> C7
5) Bring up Diag1, add a navigable association from C7 -> C8
   (see screenshot1)
6) In Diag2, select C7 and delete this imported element, select "remove from imported element"
   (concurrentModificationException is seen as reported in bug #119952),  I have to delete twice
   to remove it from the imported element list
7) In P1, expand C7 node, notice that association C9 still exists after removal of imported element C7
   In P2, expand C9 node, association C7 exists
   (see screenshot2)
8) Restart IDE,  in P1, expand C7 node,  association C9 is now gone. There is refresh issue here.
   (see screenshot3)
9) In P2,  association C7 still exists under C9 (as seen in screenshot3), attempt to re-establish
   the association between C9 and C7.  In diagram Diag2,  delete C9 from the diagram ONLY.
   (see screenshot4)
10) DnD C7 from P1 to Diag2,  DnD C9 from P2 to Diag2, the navigable association from C9 -> C7 is
   missing in the diagram Diag2 though it exists in the project tree P2
   (see screenshot5)

   This is inconsistent in the UI vs the Projects tree.  The issue is that relationship is not
   being recovered after removing imported element and re-importing the same element.  Relationship
   cannot be re-established via the UI.