World map graphics problem!!!

[dagedag]

After leaving a city, castle or a town, sometimes my world map turns like this:http://cloud.steampowered.com/ugc/594716531748448682/4D4A1F99B4E2B2983A10163C7B3E3D710C9A290B/

does anyone have this problem too?
more importantly, how can I fix this?

 

[wrc]

Update your graphic driver or try playing in dx7 mode.