Error adding new branch (due to locked subpackes)

[tlaue]

I have a version controlled project with nested sub packges and want to add a new branch to version control (Version Control of Team Foundation Server).
After Clicking "Add branch toi version cotrol ..." I get the error message "Some of the packges in the selected branch are locked. They cannot be version controlled at this time."
I cannot find any locked packages. What is the technical reason for this message.
I am using Enterprise Architect 7.1.830

For further development of EA I think it would be helpful to get any further information in this case (which packages are locked or something like this).

[Nicholas]

Possible answer: I get this message if the parent package I am adding the branch under is not checked out.  I check out the parent and the message goes away.