Ok, Im running Mandriva 2006. Ive installed the newest drivers from the ATI website, only when I reboot, for some reason, it goes back to the Mesa libraries, which means no 3-D acceleration, and other stuff. So, here is my xorg.cong:
# === ATI device section ===

Section "Device"
Identifier "ATI Graphics Adapter"
Driver "fglrx"
Screen 0
BusID "PCI:1:0:0" # vendor=1002, device=4c66
Option "FSAAMSPosY1" "0.000000"
Option "StereoSyncEnable" "1"
Option "CapabilitiesEx" "0x00000000"
Option "RenderAccel" "true"
Option "AllowGLXWithComposite" "true"

# ### generic DRI settings ###
# === disable PnP Monitor ===
#Option "NoDDC"
Option "FSAAMSPosX5" "0.000000"
Option "FSAAMSPosX2" "0.000000"
Option "FSAAMSPosY4" "0.000000"

# === Pseudo Color Visuals (8-bit visuals) ===
Option "PseudoColorVisuals" "off"
Option "FSAAMSPosX4" "0.000000"
Option "FSAAMSPosY0" "0.000000"
Option "FSAADisableGamma" "no"

# === Video Overlay for the Xv extension ===
Option "VideoOverlay" "on"
Option "GammaCorrectionII" "0x00000000"
Option "ForceGenericCPU" "no"

# === misc DRI settings ===
Option "mtrr" "off" # disable DRI mtrr mapper, driver has its own code for mtrr

# === Center Mode (Laptops only) ===
Option "CenterMode" "off"
Option "FSAAMSPosY5" "0.000000"

# === OpenGL Overlay ===
# Note: When OpenGL Overlay is enabled, Video Overlay
# will be disabled automatically
Option "OpenGLOverlay" "off"
Option "FSAACustomizeMSPos" "no"
Option "FSAAScale" "1"

# ### FireGL DDX driver module specific settings ###
# === Screen Management ===
Option "DesktopSetup" "(null)"

# === FSAA Management ===
Option "FSAAEnable" "no"
Option "no_dri" "no"
Option "FSAAMSPosX0" "0.000000"
Option "GammaCorrectionI" "0x00000000"
Option "UseInternalAGPGART" "yes"
Option "BlockSignalsOnLock" "on"
Option "FSAAMSPosX1" "0.000000"

# === disable/enable XAA/DRI ===
Option "no_accel" "no"

# === Misc Options ===
Option "UseFastTLS" "0"
Option "FSAAMSPosY3" "0.000000"

# === OpenGL specific profiles/settings ===
Option "Capabilities" "0x00000000"
Option "FSAAMSPosY2" "0.000000"

# === QBS Management ===
Option "Stereo" "off"
Option "ScreenOverlap" "0"
Option "FSAAMSPosX3" "0.000000"
EndSection
#

and the output from fglrxinfo:
Xlib: extension "XFree86-DRI" missing on display ":0.0".
display: :0.0 screen: 0
OpenGL vendor string: Mesa project: www.mesa3d.org
OpenGL renderer string: Mesa GLX Indirect
OpenGL version string: 1.2 (1.5 Mesa 6.3.1)

Any suggestions?

Check dmesg - sounds like fglrx isn't built, or is in the wrong location.
We saw something similar recently in Gentoo, but was a Gentoo-specific build issue.

I figured it out. Looks like the composite manager fubar's the driver for some reason, and it falls back to the mesa driver.