Odd Isolated Commenting Problem… Help?

I have an odd situation. We have a group of bloggers within a “network.” However, each blog is its own standalone domain.

Some sit on their own ips, some shared, all hosted under the parameter of the initial IP assigned at the 1and1 hosting service.

There is just one person within this framework of blogs who cannot post a comment on any other blog but only within just this circle of blogs.

I cannot duplicate her issue since I am also on the server, yet I am able to post on anyone’s blog regardless of their ip.

The person having the problem has no trouble posting OUTSIDE our network.

This may be a firewall issue? But since it involves commenting using wordpress, I’m hoping there is a genius here with some solutions or possibilities to check so she can post everywhere.

Thanks ahead of time for your time!