--- Operating System, Graphics card ---

Debian Squeeze 64-bit / nVidia 8600 GT
Also tested on Ubuntu 12.04 with integrated graphics card.


--- Blender version with error, and version that worked ---

Bug is always reproducible with Blender Linux official version 2.68, 64-bit.
It never occurs with Blender 2.67b.


--- Short description of error ---

Blender crashes with an ocean and a subdivision surface modifiers attached to a plane when trying to move the subdiv surface modifier above the ocean modifier in the stack.

--- Steps for others to reproduce the error (preferably based on attached .blend file) ---

1. Create a polygon plane. Go to modifiers, attach an ocean modifier to the plane and change it to displace mode.
2. Add another modifier to the plane - a subdivision surface modifier.
3. Try to move the subdiv surface modifier above the ocean modifier in the stack. Blender crashes. This is reproducible every time, on two different 64-bit machines.