unable to use the radeonhd driver

[bsdaddict]

Hi,
I'm using pc-bsd 7.1 with a Radeon X1650 Pro (RV535) graphics card. But I can only use it with the Vesa driver, not with the radeonhd driver. The X-server doesn't start (from my /var/log/messages) :
...
Apr 23 20:14:17 bsdaddict kernel: drm0: <ATI Radeon X1650> on vgapci0
Apr 23 20:14:17 bsdaddict kernel: vgapci0: child drm0 requested pci_enable_busmaster
Apr 23 20:14:17 bsdaddict kernel: info: [drm] AGP at 0xf0000000 128MB
Apr 23 20:14:17 bsdaddict kernel: info: [drm] Initialized radeon 1.29.0 20080528
Apr 23 20:14:17 bsdaddict kdm-bin[1575]: X server died during startup
Apr 23 20:14:17 bsdaddict kdm-bin[1575]: X server for display :0 cannot be started, session disabled
Apr 23 20:14:19 bsdaddict kdm-bin[1644]: X server died during startup
Apr 23 20:14:19 bsdaddict kdm-bin[1644]: X server for display :0 cannot be started, session disabled
Apr 23 20:14:21 bsdaddict kdm-bin[1684]: X server died during startup
Apr 23 20:14:21 bsdaddict kdm-bin[1684]: X server for display :0 cannot be started, session disabled
Apr 23 20:14:23 bsdaddict kdm-bin[1708]: X server died during startup
Apr 23 20:14:23 bsdaddict kdm-bin[1708]: X server for display :0 cannot be started, session disabled
Apr 23 20:14:25 bsdaddict kdm-bin[1731]: X server died during startup
Apr 23 20:14:25 bsdaddict kdm-bin[1731]: X server for display :0 cannot be started, session disabled
Apr 23 20:14:25 bsdaddict init: getty repeating too quickly on port /dev/ttyv8, sleeping 30 secs
...
Every time I try to use the radeonhd driver, X won't take it and returns me to the screen where I have to take the vesa.
Any hints or help on how to get my Radeon card working with the radeonhd driver ?
Thanks.