With two different monitors and three different cables (hdmi, vga, and dvi), my screen video gets goofed up when exiting X when using the radeonhd driver. This does not occur using fglrx.
I've seen it once - was radeon not hd and I'd been messing around switching between drivers/using svideo so I didn't consider doing a bug report.
If you can always reproduce it from a power down and fglrx is uninstalled then look in your /var/log/Xorg.0.log - somewhere there is a line with your card pciids that you can use as a subject line for emailing a bugreport to the radeonhd list (address is also in the log).