Pegasus- Do you have your blog set up so that only subscribers can reply?

My only ideas:
1. log on to your admin panel click on the options tab and under the general section there is a check box marked membership. I think you want that unchecked.
2. Still under options look for the sub-tab marked discussion. check to make sure that all boxes that need to be checked are checked. You definitely need the one that says "allow people to make comments" checked

That's all I can think of right now. Let me know if you need any further clarification or if that doesn't help.