Are you still having this problem? I just confirmed that the basic cookie achievement worked just fine for me and I didn't have the forever spinning issue. You may also want to try clearing your browser cache and see if that helps, since sometimes that step can fix strange issues.

For discussion about the cookie drop rates, please take those to a more appropriate place - this thread is really meant for problems with the achievement itself!

Are you able to try in a different Internet browser to see if it's just one browser, or all of them?