After you burn the CD, look at its contents. You should see a single file in the root directory named LNFA1091.ESU
If you do not see a single file with that name in the root directory of the CD, you have not followed the proper procedure for creating the disc.
Remember that the .RAR file is a compressed archive which must be unpacked
to create the firmware file, LNFA1091.ESU. You must use UNRAR or similar
utility to do this. The file you downloaded cannot be used "as is" - it must be unpacked first.
You then need to make a DATA CD in ISO-9660 format containing that one file - LNFA1091.ESU. This is NOT the same as burning a disc from an .ISO fiile. (Sorry if you alreay know this, but it must be eliminated as a potential source of error).
If you do see that file in the root, and the 5005 will not load it, do a binary compare with the original source on your hard drive. They should be identical. If the 5005 still won't load it, try burning using a different brand of blank, and burn at a slow speed (4X).
If the 5005 still won't recognize it, I'm out of ideas. Either the firmware is not the proper one for your machine, or the machine is having trouble reading discs.