Hi,
I believe it's a "run once" flaw in in the ATI Display Driver
setup/installation (the one from ATI's website). If you just X out the
Display Settings' window, it seems to keep coming back. Rather than do that
the next time it occurs, make some temporary change to a setting in the
window, so that the Apply button is no longer grayed out, then switch your
change back to the way it was, and then click Apply > OK. (E.g., change the
color from 32 bit to 16 bit, and then back to 32 bit.) This should give the
ATI Control Panel what it wants, and put an end to that window popping up at
boot.
Hope this helps,
Dean