Ok. Finally something I can explain.
A 406 means that the file is too large. What PHP and .htaccess report are COMPLETELY different. Many times, a host puts a restriction on the bandwith, usually 2 MB, 5 MB, or 10 MB. Many hosts do this so they are not flooded with data.
Either get a better plan with larger bandwidth, (GoDaddy doesn't as far as I know, give out 1GB uploads.)
or host your own server and set your own bandwidth size.
If you are the one trying to upload this file, try to put it using FTP in the store/ folder and link to it, so people can download.
If someone else is trying to upload this file, try to get the file from them, or give them an FTP account to upload. DELETE THE ACCOUNT WHEN THE USER IS DONE! Tell them to link to the file.
Disclaimer: I am NOT responsible for damages to any board but my own. If something goes wrong, I'm not responsible. It is YOUR decision to do what YOU want to do with YOUR board.
YOU HAVE BEEN WARNED!