Display Properties problem in RC1

Since installing RC1, when I unckeck "Hide Modes that this monitor cannot
display" in the advanced section of display properties, I am initially able
to get the 1776 X 1000 (1080i) I need, but after using Media Center or
rebooting, the resolution resets to a "safe" resolution. When I go into
display properties again, the Hide Modes box is again checked. This did not
happen in Beta 2 or 5534, and I was able to have my resoution continually set
to 1080i. I am using an ATI Radeon X1300 hooked up to a Sony HDTV via DVI to
HDMI, and I've tried using ATI's RC1 drivers, but the problem persists. Any
help would be greatly appreciated, as everything else is running very
smoothly. Thanks.