Edit: After half day, my wife’s Mac started having the same problem. I have then applied the solution that I found in the Apple
iOS 6 New Maps Do Not Impress Users
So yesterday Apple released iOS 6 to the public and 24 hours the public reviews are coming in and especially bad reviews for the new Apple maps. All earlier versions of iOS hand shipped with Google maps built in but Apple decided it was time for change and shipped iOS 6 with Apple’s very own maps.
As you can see from the images above it is no were near the standard of Google maps yet. If we take a look at the image on the right it shows York city in the UK and as you can see 3 quarters of the city loads in black and white and the other quarter does not bother loading. You can also see on the left the poor 3d modelling of Brooklyn bridge which looks like a wavy line.
Do not be expecting any of this to change in the next few hours or days as creating maps and 3D maps take an extremely long time but we are sure Apple is trying its best to resolve the issue. Apple was also hit with some problems yesterday due to iOS 6 with users being unable to use WiFi and also not being able to access Passbook