Same problem I saw and an another dnx 5260bt of a friend of mine.... at February 2013...

ALL maps with typ file (custom or not) had that problem (Autodrive - Anavasi - City with my custom typ)

Solution was only empty typ file....

Last week I updated maps at that machine... and I tried to put typ file with polygons and empty polylines, or polylines with empty polygons... Same problem....

The only solution I didn't tried is empty polylines and transparent polygons.... next time I will try that.. and I will say here what happened