A little late, but for anyone still troubled by this:
nm_geo is correct. It is NOT a video card issue. The problem is that the b43 driver for the Broadcom wireless needs code from Broadcom's proprietary firmware. The fact that this halts the boot process is just bad OS design.
When the LiveCD presents the boot prompt, boot with
to prevent the b43 module from loading, erring out, and halting the boot. The wifi will be unavailable, but at least the OS will load. If you can get networking via some other hardware, e.g. ethernet, then you can use the instructions and downloads here: http://linuxwireless.org/en/users/Drivers/b43/ to get wifi working.
boot: live modprobe.blacklist=b43
If this does not work for you, you may need to use
instead. VERY old OS versions may need
boot: live modprobe.blacklist=b43legacy
boot: live modprobe.blacklist=bcm43xx