problem with git gui on cygwin.

I have been trying to use git for a small project using cygwin.  I copied my
repository from one windows XP system to a Vista system using a usb drive.  On
the new system when I use "git gui" I get a pop up that says "Git directory not
found: .git"

This happens with git gui and gitk.  The command line programs I tried, git show
and git status appear to work.

I updated cygwin and have git version 1.6.0.2.

Does anyone know what the problem is?