Mouse wheel problems on PMDG777

Hi guys

I've a problems of my PMDG777 with SP1

When I adjustment IAS HDG V/S and ALTITUDE of MCP panel knob with mouse wheel,the mouse wheel can't be scroll on knob,but that can use in the panle below MCP somewhere.

Is that a bug?How can I fix't?

I try to reinstall the FSX and PMDG,but that still not work.

thanks for your help