Is there any info. on the pump as to how much amperage it draws? It sounds like you are tripping an overload protector on the power supply. When it cools down and resets you can power it up again and it will work fine but if the pump is rated for anything over 1 amp (1000 milliamps) it will keep happening.
Come and get one in the yarbles, if ya have any yarbles, you eunuch jelly thou!