The basemap isn't old and it wouldn't matter much if it was, but it's the latest one anyway.

What is more likely than the basemap causing you grief is possibly a problem with either your detail map or the JCV file or even maybe your POIs. Back them up and replace them with fresh downloads. But first try clearing NV after you back up your gpx folder [if it's important to you]. To clear NV: From the Map screen, press 'Speed', then press and hold in the centre of the Speedometer for several seconds>Developer Info>Nonvol Available>Clear Nonvol. This is even more comprehensive than a Hard Reset and will virtually take the unit back to Factory Settings. Also, has the unit got V6.20 fw? If it has reload it with WebUpdater anyway, if it's earlier definitely update it after the clear NV. Then clear NV again after the fw is reloaded or updated.

That wasn't what I asked you about the charger's desctiption. What i mean is that some cheap non-genuine chargers will throw the unit into Mass Storage mode temporarily. A genuine Garmin car charger will never do that unless it's faulty.