What I am doing:

1. Apply external properties to a folder in the trunk (both single file and folder external, externals are binary files)
2. Create a branch from the trunk and update the entire project
3. Modify a file on the branch and commit the changes, then update the entire project.
4. Merge -> "Reintegrate a branch" when I get to the last screen I click "test merge" and get this error:

> 
> Error: Cannot reintegrate into mixed-revision working copy; try updating first 
> 
> 
>

I update the entire project and still the same error.

Other observations:

* If I "Merge a range of revisions" everything works fine.
* If I remove the externals everything works fine using either "Merge a range of revisions" or "Reintegrate a branch".

How do I solve this issue?

I am using Subversion 1.6.6 with [TortoiseSVN](http://en.wikipedia.org/wiki/TortoiseSVN) 1.6.6.