1) The only way to "force" it to go to the new location is to let it sit with a view of the sky until it locks onto the GPS satellites. It may take some time if you're quite far away from where it last had a satellite lock.
2) What you've explained there sounds like what my nuvi does when I set it to "Off Road". Are you using City Navigator maps or have it set to the "Automotive" profile perchance?
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