xorg and radeon, widescreen

[Max Russell]

I'm having issues with my X1350, video7 flatscreen and xorg.conf - the
relevant sections of my xorg follow:

Section "ServerLayout"
    Identifier     "X.org Configured"
    Screen      0  "Screen0" 0 0
    InputDevice    "Mouse0" "CorePointer"
    InputDevice    "Keyboard0" "CoreKeyboard"
EndSection

Section "Files"
    RgbPath      "/usr/local/share/X11/rgb"
    ModulePath   "/usr/local/lib/xorg/modules"
    FontPath     "/usr/local/lib/X11/fonts/misc/"
    FontPath     "/usr/local/lib/X11/fonts/TTF/"
    FontPath     "/usr/local/lib/X11/fonts/OTF"
    FontPath     "/usr/local/lib/X11/fonts/Type1/"
    FontPath     "/usr/local/lib/X11/fonts/100dpi/"
    FontPath     "/usr/local/lib/X11/fonts/75dpi/"
    FontPath     "/usr/local/lib/X11/fonts/URW/"
EndSection

Section "Module"
    Load  "GLcore"
    Load  "dbe"
    Load  "dri"
    Load  "extmod"
    Load  "glx"
    Load  "record"
    Load  "xtrap"
    Load  "freetype"
    Load  "type1"
EndSection

Section "Monitor"
    Identifier   "Monitor0"
    VendorName   "VideoSeven"
    ModelName    "R19W01"
    Modeline "1440x900_60.00"  106.47  1440 1520 1672 1904  900 901 904 932
-HSync +Vsync
EndSection

Section "Device"
        ### Available Driver options are:-
        ### Values: <i>: integer, <f>: float, <bool>: "True"/"False",
        ### <string>: "String", <freq>: "<f> Hz/kHz/MHz"
        ### [arg]: arg optional
        #Option     "ShadowFB"               # [<bool>]
        #Option     "DefaultRefresh"         # [<bool>]
        #Option     "ModeSetClearScreen"     # [<bool>]
    Identifier  "Card0"
    Driver      "vesa"
    VendorName  "ATI Technologies Inc"
    BoardName   "RV515 [Radeon X1300]"
    BusID       "PCI:2:0:0"
EndSection

Section "Screen"
    Identifier "Screen0"
    Device     "Card0"
    Monitor    "Monitor0"
    DefaultDepth 24
    SubSection "Display"
        Viewport   0 0
        Depth     1
    EndSubSection
    SubSection "Display"
        Viewport   0 0
        Depth     4
    EndSubSection
    SubSection "Display"
        Viewport   0 0
        Depth     8
    EndSubSection
    SubSection "Display"
        Viewport   0 0
        Depth     15
    EndSubSection
    SubSection "Display"
        Viewport   0 0
        Depth     16
    EndSubSection
    SubSection "Display"
        Viewport   0 0
        Depth     24
        Modes "1440x900_60"
    EndSubSection
EndSection

this fails to start x with the /var/log entry reading -
(WW) RADEON: No matching Device section for instance (BusID PCI:2:0:1) found
(EE) No devices detected.

Fatal server error:
no screens found

It has been suggested to me that I comment out the BusID entry, however I am
unsure as to why this should work?