Land Vanishes After Placing Lot (blue rectangles)

This is primarily an issue when using Create a World but it has happend once in Edit Town.  When I go and place a new lot in various areas on the world the lot appears but much of the surrounding terrain vanishes leaving large blue rectangles in its place.  If I delete the lot the blue goes away and if I move the lot  and get lucky the blue goes away.  Additionally If I move an otherwise fine lot to a problem spot the blue appears.  This happens in the Create a World tool as well as the edit in game function.  

I have searched for similar problems and all I could find was information revovling around zoom+/- causing blue boxes. And I have tried ajusting settings under veiw. 

I use a PC with Windows 7 and an Intel Pentium.

If anyone can help it would be much apreciated.