bcm43xx-fwcutter issues, FC5, x86_64

[Mike Lease]

I've been spending several days trying to get my wireless card working 
under FC5 x86_64 on my HP Pavilion zv6000 laptop (it works fine under 
WinXP Pro).  It is set up as a dual-boot system, it has an Athlon 64 
3200 processor, a Broadcom 4318 AirForce 54g wireless card, and 1 GB of 
RAM.  I've reinstalled FC5 twice in the course of debugging this 
problem.  After the installations, I've done "yum -y update" and "yum -y 
install bcm43xx-fwcutter".  However, on my most recent iteration, when I 
try to run fwcutter on any of several firmware files I've downloaded, I get

"Sorry, the input file is either wrong or not supported by bcm43xx-fwcutter.
I can't find the MD5sum <hex strings> :("

...where <hex string> changes depending on which files I'm working with. 
  I've downloaded all sorts of files advertised as 64-bit Broadcom 
drivers, but at this point, I get the above with any of them.  During 
previous tries, I've tried ndiswrapper and wpa_supplicant as well; I did 
refrain from doing anything with those this time around, as someone on 
one of the forums I found (possibly this one; I don't remember) 
suggested that trying to get them to work might leave junk around 
interfering with the native support.  I don't believe I had this problem 
with fwcutter before.

I have seen suggestions to use the 32-bit version, but I'd rather not; I 
got a 64-bit system so I could use it as such.  I do want to use WPA, 
but since I'm not even getting fwcutter to work, that's not really 
relevant just now.

Does anyone know what the above message means, and how I can fix it?

Thanks for any assistance,
Mike