We have this same setup, we use almost exclusively Polycom 331s, and provision via DHCP option 66. I have never seen this error. However, we're on v12.5 still, haven't upgraded to v14 yet. I assume you're starting with v14?
Did you set everything up according to the description here: http://www.3cx.com/sip-phones/polycom-soundpoint-450-550-560-650-670/ ? My initial guess is that not all of the Polycom firmware contents were put in the provisioning folder, because after the sip.ld it should move on to download other config files, but if they're not there it would choke. Or maybe some of your config files don't match? Or maybe one is corrupted or has been changed and isn't valid anymore?
I believe that the Polycom FAQ that would apply here is http://community.polycom.com/t5/VoIP/FAQ-What-does-the-message-quot-Config-file-error-Error-is-lt-Hex/td-p/30464 , it might give you something to go on, too.