Marineland Magnum 350 Troubleshoot

[ksolmen]

At the office where I work, one of the employees was cleaning the goldfish tank and did not turn the filter off. The filter stopped working and we are unable to get the flow back up. Both the intake and output tubes are full and the motor is running, but there is just no flow. Any suggestions? I've been trying to avoid doing a complete disassemble.

[Fresh2o]

Are there any flow control valves present, and, if so, are they completely open?