UBB.threads PHP Forum Software Community Forums UBB.threads 7 Version 7 Support Posting restrictions on new install

I have a test user who is trying to post a message on my new 7.1 forum and he is receiving this message:
"The host from which you are accessing the board is not recognized as a valid host. This is more than likely related to a firewall issue that is blocking the referer variable. Check your firewall settings and try again. "

She says that she is not using a firewall. What else that can be?
I can post message (as a user) from here w/o any restrictions.

If I disable the 'Refer' check mark on the Admin, what else I will loose?

Just disable the refferer check,
it helps prevent spam that's all.

Mines Off

Yes, the short fix to subverting this error is to disable this setting.

The setting is there as a spam prevention feature; basically if the referrer variable cannot be read it spews this error; generally this happens when the user is using a firewall or security suite (or browser plugin) which filters out this variable.