Thanks mkossmann,

Yes...well it tried. But the 'gksu-run-helper' was not in the path so it failed. Fortunately, the dialog displayed the command it was trying to run, so I just copied it and ran it from the command line...and it worked fine. As an added plus, I can incorporate that command directly into my automatic kernel build script. Here it is, if anybody wants to do the same:

'/usr/bin/vmware-modconfig' --icon='vmware-workstation' --appname='VMware Workstation' --gcc='/usr/bin/gcc' --headers='/lib/modules/2.6.25-gentoo-r8/build/include' --gcc-ignore-minor

You need to adjust for you kernel header path, but other than that, this will do the trick. Thanks for the responses.