Makerbot layer thickness
Unlike PLA, PETG does not like to be "squidged" down, it likes to be laid down. If you use too small a layer height, there is the danger of the filament sticking to the nozzle, rather than the bed (or filament already laid down). Try using a larger layer height -- between 0.2mm and 0.3mm, if you have a 0.4mm nozzle.