One dose of garlic is not going to cure your new damsel of ick. That the spots have started to go away is the sign they have gone into the reproductive stage and will appear again in several days.
Here are links about ick posted at the beginning of this thread:
http://www.advancedaquarist.com/issu...2003/mini1.htm
http://www.advancedaquarist.com/issu...2003/mini2.htm
http://www.advancedaquarist.com/issu...2004/mini3.htm
HTH.