PC Chips m811 & Radeon X1600 compatability problem

[Kusaywa]

I have a PC Chips M811 MB and when my NVidia Geforce 2 Pro AGP is installed it starts up fine. When I recently installed a Radeon X1600, it wouldn't start. If I held in the start button to turn off PC, and then tried to start, it would start and run fine after that. The X1600 is a 8X AGP and the NVidia is a 4X (I believe). The MB is only supposed to use a 4X but the X1600, once started, runs fine. There is no bios update for this board, and I would love to use the X1600, but it's my kids computer and the startup problem is frustrating (he's 6). There is nothing in the bios to change to 8X, only 2 & 4. Is there a way around this problem?