Strange behaviour - CUDA program woking with driver 275, but not with 280.26 Using driver 280.26 the

Dear All,

in the last times I have encountered a very strange problem. I am developing a CFD program for CUDA. The program has been working fine for 2 years now. Today, I have refreshed the graphics driver to 280.26, and the program does not work anymore. Or to be precise, the program works, but the iterative behaviour in it does not converge anymore. 
 Has anyone seen something like this before?

                        Best regards,