Thank wr104 you for the hint about deleting the .bin file! I now successfully disabled opencl optimization and my ASUS r9 290 bumped from 150Khps to the current 291Khps @ about 90C°/ 2200 RPM. I suppose I should "tweak down" the thing a little bit...

Oh, but did I dream or the walled briefly said it wanted an update? I'm running  v0.5.0.0-g0-beta (64-bit) . I went out to check a newer version and now the message has disappeared. MD5 of my install file is 87b1557e2d4cbf8c95616b48c34ff537 (as well as the latest I could find linked in the homepage)

Ok maybe it's my brain that can't sustain all that heat! :-D