This Graphics Card does not meet Minimum Requirements for Shader Support

I have a GeForce 560 Ti, which used to work perfectly for FSX.

However, after a couple of months away, when I try to start FSX, I get the above message.  The card still works pefectly for everything else (MS Office, XPlane 10, Skyrim etc).

I am using driver 335.23.

Does anybody have any ideas what's gone wrong & how to resolve the situation?

Thanks.