Process.Start() exits right away on Windows 7

Process.Start("d:/test.txt"); //simple .txt file works perfectly fine on Windows 8 onward but on Windows 7 (x64) it starts the process and immediately closes it.

I've already tried the following:

1. Calling through ProcessStartInfo and setting CreateNoWindow=true, UseShellExecute=true and Verb="runas" (though not sure why I had to set this one).

2. Tried attaching Exit event and it confirms that the process does start but it exits right away and I don't even see the Notepad window open for a blink of a second.

Edit: I've tried it with an image files and few other extensions and they open just perfect. Something wrong with just the .txt files (and/or probably other formats).