Quote - > Quote - Quick question.. when I am setting the OpenCL workgroup Size what exactly is that doing or using?

It's giving a fix to a bug in the nVidia driver. Normally the driver should be able to set a good default for that internal value but it turns out that it does not happen. It's related to memory allocation at the beginning of the task, if I remember well. 

Thank you for answering ^_^ .. so I set it to 64 and all works ..  to well :D