ATI - HDTV primary monitor - input change freezes computer

[George72]

I have a 4670 Sapphire with 1GB mem. I've encountered problems when I change the input on the HDTV (Sharp aquos 32D64u) or turn off the television power. When I return to the HDMI input or turn the TV back on, the computer appears frozen and only a hard reboot is possible.

WinXP Media edition
Up to date drivers (9.6)
Saphire 4670 with HDMI output

If I've neglected some required specs, let me know.

Thanks