This happened to me about a month ago, and was very frustrating!
After checking the prongs, freezing my wall wart, etc. etc., my 13 year old son came in my bedroom and asked what was going on? (he could see I was messing around with my charger/Prime)
He then pulled apart the wall wart (it apparently can use either a UK plug or a U.S. plug, and the two plugs simply slide into the wall wart), pressed the two parts together again, and told me to try it.
Sure enough, it worked! (kids!)
If that doesn't work, Office Depot does have the Asus chargers for the Tranformer Prime, Transformer and TF300 in stock, at least in my area.