All devices which have both water and electric need to have a protective GROUND wire. That is the green wire you have. BE SURE IT IS CONNECTED TO GROUND (Not neutral)
Here is a link for the part you are looking for:
http://www.searspartsdirect.com/partsdirect/part-model/Carrier-Parts/Humidifier-Parts/Model-HUMCCLBP2317A/3079/0913000/50027453/00001?blt=06&prst=&shdMod=
Chances are it's from the condesate tubes or collector box. If not, you may have a cracked A/C drain pan- lots of installers over tighten the male adapter into them and cause cracks. next check to see if they installed all the condensate plugs at install, some installers don't- read the manual in the "how to set up the condesate" section and trace EVERY tube to make sure they are routed correctly and not cracked/ cut/ nicked. Most furnaces are multi-position now and some installers don't move every tube nessessary... Hope this helps, if not, post a close-up pic, and I'll pinpoint the bad spot for you...
