Good news: no enema needed for this repair! Sublime Master SANTA turns up the heat on this one:

The first thing to do is undo the water line connection that is below the left bottom of the freezer door, might have to remove the kick plate. Then press the dispenser and see if you have water pressure to that point. If you do then you can test the frozen water tube theory by using a hair dryer to warm up the water tube area for about 10-15 minutes with the door open and see if it thaws out. Be careful not to melt the plastic with the hair dryer. I've noticed alot of times it's a small amount of ice that thaws out by the time I get the heater kit installed. I'll get back to you with the part # of that kit...

Found it ==> http://www.repaircli...9X10173/1381601

Source: GE ZISB480DMC Water dispenser