I saw over at Rage3D that ATI made an official response regarding the Radeon 9700 AGP 8x compatibility issues which users have been experiencing over the past month.
ATI is aware of a small number of reports of incompatibility between the RADEON 9700 PRO graphics accelerator and certain AGP 8X motherboards. It is important to emphasize that the number of incidents is very low. Extensive testing has been done, in conjunction with motherboard chipset manufacturers, motherboard manufacturers and with retail available motherboards, to determine if compatibility issues exists. From these tests, it has been concluded that no compatibility issues exist with the current or soon to be released AGP 8X motherboards.More information at Rage3D
Some end users have reported issues to our Customer Service department that we are investigating. From the data that has been gathered, it appears that issues that have been reported are caused by individual board issues and are not indicative of a general compatibility issue. RADEON 9700 PRO product owners are encouraged to contact our Customer Service Department should they have an operational problem with their product.
In addition, it is important to ensure that appropriate system preparation is done prior to installing the RADEON 9700 PRO. We recommend installing the latest motherboard BIOS in the system as well as the latest available AGP drivers. Many of the 8X issues have been resolved with an updated BIOS from the motherboard manufacturer.