"The best business telephones in the world."

Attempting to set up Snom821 using WLAN feature.  I am using a BIGtec BIG120 USB wireless adaptor.

I have followed the Snomwiki instructions to do so i.e uploading the latest firmware version, putting the stick in, scanning the networks, doing the network config for the network that shows up , saving that successfully, pulling out ethernet, rebooting as instructed...

When the phone boots back up, it goes through the usual steps with the IP address, MAC code etc but then it keeps trying to provision, but eventually just goes to to default phone home page with the message "provisioning server failed".  Date and time revert to 1/1/1970 00:00.

Any ideas what might be the issue here?  The phone works fine when hard wired via ethernet.

Thanks

Chris