Unlock Linksys Sipura SPA 2102, I am able to unlock it and use it with my own voip provider, but with slightly different step.
1. without connecting it anywhere, except a phone headset, set device to default configuration, by pressing **** and option 73738# and press 1 to confirm.
2. make dns record to have us-prov.clearwire.com pointing out to personal webserver address.
3. and copy that spaMAC.cfg which is explained in above link to webserver directory.
4. turn on SPA device, and after it get the provision file above the device will have all password cleared.
easy device to work with.