I Can't Unload Filament
If the filament is stuck in your extruder, try manually unloading it using MakerBot Desktop.
Connect your MakerBot Replicator to your computer using the USB cable that came with it. In MakerBot Desktop, open the print monitor panel and select Change > Load. Wait for the extruder to heat. Push down on the filament that is loaded in the extruder until you see plastic emerging from the extruder nozzle. You should now be able to unload by selecting Change > Unload in MakerBot Desktop.
If you are still having issues unloading filament, it may be time to clean your drive gear. Follow the instructions here to learn how.