Nicholas J. Michalak said:

Well, the Tantive IV was caught in the SD's tractor beam in ANH. That's how the Empire commandeered and boarded the ship. And I would think that if you tried to engage your hyperdrive while in a tractor beam, your ship would likely get ripped to pieces. Either that, or it would be like slamming on the accellerator while your wheels are locked - you're just gonna burn out the engine.

I know Adywan is ignoring the EU for the purposes of this edit, but the only thing that can stop a ship from going into hyperspace is an interdictor field - tractor beams are comparatively weak. Just a thought.