Existing Git projects without an existing .gitignore file, if opened in Visual Studio 2010, cause an exception when selecting "Open .gitignore".

Steps to repeat:
1) Create a Git repository and Visual Studio project.
2) If a .gitignore file was created, delete it. (Some tools don't create one by default.)
3) Open the project in Visual Studio.
4) Right click on the solution, the project, or a file in the project.
5) Select Git (master) -> Open .gitignore

A message box should appear with the following message:
"The parameter is incorrect. (Exception from HRESULT: 0x80070057 (E_INVALIDARG))"

We've tested this on a couple of machines, all of them running Win7 Enterprise 64-bit.