You can try a hard reset, if you'd like but I have never seen it resolve this issue. Unfortunately, it has been happening to many Garmin folks lately.
Here is the hard reset procedure...
In order to save your user-entered data, please do the following: (If you don't really have any that you really need to save, you can skip this section...)
1. Hook your Nuvi up to your computer, then double click on "Computer" (Vista / Windows 7) or "My Computer" (XP), then double-click on your "Garmin" or "Nuvi" drive.
2. Copy '/Garmin/GPX/current.gpx' to a place on your computer where you will be able
to find it later.
3. After the hard reset is complete (below), go ahead and find your backed up 'current.gpx' from that place you saved it to in step 2. and rename it to temp.gpx
Then, put it back in the '/Garmin/GPX/' folder on the Nuvi.
4. The next time you turn your GPS on, that file will be read from temp.gpx and restored to your GPS so that they'll be available to you to access again.
Start with the unit off and unplugged from USB cables, charger, etc.
Touch and hold the lower right corner of the screen with an index finger or the eraser end of a pencil.
Continue pressing the lower right hand corner of the screen with your finger, then power the unit on.
Release the power button when the device powers on.
You will see a message that says, "Do you really want to erase all user data?"
At this point, you can remove your finger from the touchscreen and touch "Yes"
Your Nuvi will reset at this time. Follow the on screen prompts, then place your device in an area with a clear view of the sky until it acquires satellites.
I hope that resolves the calibration problem you're having...if not, I am afraid there isn't much more we can do to fix it and we'll need to look into getting it repaired for you.