Comment issues

Ok so I've realized I have a problem. I have been told that a reader was unable to leave comments on my blog. I don't know if this is due to her browser settings, but once she clicked 'publish' the comment disappeared.  I do my best to reply to all comments left on my blog, so please don't take offense that I haven't replied you - I just didn't know there was a problem.  I have changed the settings to a "popup window" so, hopefully that fixes the issue.