You mean you run Linux in a virtual box in XP? If so, Linux can run many devices without the specific drivers required by Windows. I've never tried to access a Garmin device in Linux [i have Ubuntu 64-bit in VM Player on Win 8.1] but i wouldn't be surprised if it could deal with Garmin devices without squarking for drivers.
Regardless of whether it's XP or Linux in the virual box, are you absolutely sure you've got the latest Win drivers loaded to the host Windows? It would explain why you can't see the nuvi directly in it but you can in Linux or Virtual XP. Humor me, please load them again anyway:
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