Cycles (Nvidia driver lost connection)

Hello guys,

I’m relatively new here, so I hope it`s ok to open up a new thread ( I already searched in the forum for this problem).
My problem is that when rendering a quite simple scene with cycles Blender crashes and I get the information: “The Nvidia driver lost connect […] Error code: 7” (something like this)
I render an high-poly car (500 samples) and it worked fine. But in this scene Blender crashes. It consists of only 5 mid-poly buildings with image textures and around 30 very low poly buildings with textures. I cannot believe that my V-RAM is overloaded. I have an GeForce GT440 (2GB Ram)

other specs:
win7 64bit
AMD Athlon II X2 260 Processor @3.2GHz
newest Blender version

Hope you can help.
Thanks in advance.

David