Steve and I noticed a similar problem at http://wordpress.org/support/topic/352406?replies=10
SO I want to open a thread on this.
It seems that Skyban and Hughes.net cannot access WP 2.9.1 sites.
Why satellite providers are having this issue, I do not understand; perhaps they change the users ip during the session and WP boots them out.
This problem began occuring on Friday Jan 7th and is persistent.
I have had my hosting company check everything, DNS propagation, firewall settings, scripts etc....nothing on our end, we changed nothing.