Vim.app not working as expected with MacOS X 10.9 and 10.10

• Vim.app will not run on MacOS X 10.9 (Mavericks) and MacOS X 10.10 (Yosemite).

• Running "/Applications/Vim.app/Contents/MacOS/Vim'" from the Terminal works just fine.

• Running "/Applications/Vim.app/Contents/MacOS/Vim -g'" from the Terminal will(!) start Vim with the GUI.

I have no idea why the GUI will not open when double-clicking on the Vim application icon.
Any hints/help is welcome...