After clearing a paper jam,

One of the paper flags is either stuck down or broken (from the area of the jam)

After you've unplugged the printer for at least 120 seconds and plugged it back in, during the power up the printer gears and feed mechanism perform self checks / LISTEN VERY CAREFULLY FOR CLICKING OR WHAT SOUNDS LIKE CLUTCHING / if this is occurring you could very well have shards and paper slivers in the gear teeth.

Those shards prevent the mechanisms from rotating and this seizing reads out to the HP as a paper jam.

HP's are underpowered and those tiny shards are enough to seize up feed mechanisms.

This typically occurs right after a real paper jam and the user had to rip out the jammed sheet since and it those shards that can foul up the mechanism.

the only gears you need to check are the ones you can see since it is those same gears that drive the rollers that feed sheets.

Use pliers to manually turn the mechanism yourself, it any rubber roller you grip with the pliers has any resistance when rotating, then check the drive gears connected to the roller and look for shards and slivers while you manually rotate the rubber rollers.

Clean em out with any instrument sharp enough to and reset the device to see if the jam error is cleared.

Follow this link for graphical instructions:

http://www.amazon.com/gp/customer-images/view-large-image.html?imageId=22103071