It sounds like a jammed nozzle. This typically happens when the printer gets used, then idles with the filament. What you need to do is melt the remaining filament from the nozzle. If you can do this manually, it would be good as I don't think the Solidoodle machine may not suffice to preheat the remaining filament. If you can also manually remove -- pick out the filament by longnose pliers -- that would also be good.

Do you see the extruder spinning the gears freely but nothing is getting melted? If so, then it's definitely jammed nozzle. The "clunk" sound you hear is from the extruder gears pushing its best into the hot nozzle but can't since it's more than likely jammed. This has happened to us quite a few times when we've left our printers idling even for a couple of days with the filament on. We've learned that it's best to immediately remove the filament once the print job is complete.