Error using Team Foundation Server merge function

Question

When merging two code branches in Team Foundation Server I get the following error:

The given key was not present in the dictionary.

Some files are checked out and show up in "Pending Changes", but no changes are actually made.

I have a workaround:

1. Attempt to merge (fails with error)
2. Get latest from trunk
3. Undo all pending changes with "merge, edit" or "merge"
4. Merge Again (works this time)

Any ideas on what's causing this error?

Edit after answer: Seems like a bug. And it's extremely repeatable. Every single merge does it. I'll send a bug report to MS and see what happens.

Answer 1

Sounds like a bug. If you can replicate this, I recommend you contact Microsoft Support or use the Microsoft Connect bug reporting web site. I did not find any mention of this in a preliminary search.