Some video cards are sold with a slight overclock that can lead to stability and heat problems running Octane.
Try a utility such as MSI Afterburner to underclock slightly and increase the fan speed.http://event.msi.com/vga/afterburner/index.htm
The Octane demo uses cuda 4.0. While cuda is supposed to be backward compatible the very latest drivers are cuda 4.2 and may give some small problems.
For windows the drivers are -
Cuda 4.0 is >=270.81 (>=275.33 for laptops) and <286.
Cuda 4.1 is >=286.19 (>=286.16 for laptops) and <295
Cuda 4.2 are 295.51, 295.73, 296.10, 301.24